Summary of Biology doctoral thesis: Study on structural dynamics of the evergreen broadleaf forest in Hang Kia - Pa Co Nature Reserve and Xuan Son National Park

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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.

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Nội dung Text: Summary of Biology doctoral thesis: Study on structural dynamics of the evergreen broadleaf forest in Hang Kia - Pa Co Nature Reserve and Xuan Son National Park

MINISTRY OF EDUCATION VIETNAM ACADEMY AND TRAINING 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 Major: Ecology Code: 9 42 01 20 SUMMARY OF BIOLOGY DOCTORAL THESIS HA NOI - 2020
The 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 Reviewer 1: Reviewer 2: Reviewer 3: The thesis will be presented in front of the doctoral thesis council at: Graduate University of Science and Technology - Vietnam Academy of Science and Technology- 18 Hoang Quoc Viet Road, Cau Giay, Hanoi. At time ........, …………………… The thesis can be found at: - Library of Academy of Science and Technology - National Library of Vietnam
INTRODUCTION 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
very 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)
Chapter 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
addition 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.
1.2.2. 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.
- 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
2.2.1. 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
Located 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 3.2. The flora. 3.3. General remarks on the natural conditions of the study area. Shortcomings: - In Hang Kia - Pa Co Nature Reserve: the risk of illegal logging and transportation of forest products tends to increase; and the demand for timber logging for domestic purposes such as house construction and firewood is also increasing, posing great challenges 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.
CHAPTER 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 Num. Density Plot Area of HL Botanical composition (tree/ha) species 17,3 Castanopsis indica + 9,6 Garcinia fagraeoides + 6,8 1 HB01 67 608 1/9 Hopea chinensis + 5,8 Diospyros sylvatica, + 5,6 Manglietia dandyi + 54,9 others 21,8 Lithocarpus dealbatus + 16,3 Castanopsis indica + 11,6 Trema 2 HB03 56 571 1/10 orientalis + 7,8 Lithocarpus ducampii + 42,4 others 24,8 Diospyros sylvatica + 10,0 Lithocarpus dealbatus + 8,2 3 HB06 70 466 1/7 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 4 XS01 71 344 1/5 Barringtonia acutangula + 60,7 others 9,2 Saraca dives + 6,9 Bhesa 5 XS02 86 352 1/4 robusta + 6,5 Barringtonia acutangula + 77,4 others 6,6 Nephelium cuspidatum + 5,7 6 XS03 106 487 1/5 Aglaia argentea + 5,2 Wrightia tomentosa + 82,5 others
- 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
Questioning: 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: 80 Num. of species. 150 XS01 HB06 Num. of species XS02 HB03 XS03 60 HB01 100 40 50 20 Area (ha) 0 Area (ha) 0 0,4 1 0,16 0,76 0,04 0,28 0,52 0,64 0,88 0,4 1 0,76 0,04 0,16 0,28 0,52 0,64 0,88 Figure 0.1: Changes of the Figure 0.2: Changes of the species in Hang Kia - Pa Co species in Xuan Son when when the area of the PL changed 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 Num. of Density Ordinal Location HL H D species (trees/ha) 1 HB01 67 608 1/9 3.31126 0.92541 2 HB03 56 571 1/10 2.68794 0.86451
3 HB06 70 466 1/7 2.93660 0.88831 4 XS01 71 344 1/5 3.38190 0.92425 5 XS02 86 352 1/4 3.84813 0.96488 6 XS03 106 487 1/5 4.13520 0.97539 Comment: In general, Xuan Son area has a higher number of species and diversity than that of Hang Kia - Pa Co. The level of variation in diversity in the two regions is markedly different. The area of Hang Kia - Pa Co has a greater degree of variation, reflected in the indicators H and D, with a large difference.. A composite index that is the Renyi index (H). Index calculation H for the PL we obtained the results shown in Figure 4.3: HB01 6 Rényi HB03 HB06 XS01 XS02 4 XS03 2 0 0 0,25 0,5 1 2 3 4 5 6 7 8 vc Figure 0.3: Rényi diversity index chart of the PLs On the graph, the higher the curve is, the higher the diversity is. The steeper the curve, the lower the uniformity of the number of individuals in the PL species. 4.1.2. Distribution of plants according to diameter classes (N/D1.3) The distribution of the number of plants by diameter classifiication in the study area has the following characteristics: The
distribution curve of the plants by diameter classifiication has a decreasing shape. The largest number of trees gather at the first diameter category and the second diameter category, then decrease gradually. Compare between 2 structures N/D1.3 in the two study areas, it was found that: in the study area more or less there was human influence to change the inherent natural structure of the forest. The mean diameter in Xuan Son National Park is much larger than that of Hang Kia - Pa Co conservation area. 4.1.3. Distribution of plants according to height level (N/Hvn) Experimental results using 3 mathematical functions: Meyer, Weibull and Distance to describe the distribution of plants by height level in the study area shows: there is no function suitable to describe the distribution N/Hvn in the area of Hang Kia - Pa Co. In Xuan Son area, Weilbul function can be used to simulate the N/Hvn distribution. Reality shows that, in the PL in state IIIB and state IV, the secondary layer is divided into 3 distinct layers. In the PL of state IIIA, the forest layers form a continuous block, not clearly distinguish between layers A1, A2, A3. In Xuan Son National Park, the difference between the tree layer in the canopy layer and the upper canopy layer, the lower canopy layer is smaller than that in the Hang Kia - Pa Co area. Basically, state IIIB, IV forest protection still retains the inherent secondary strata structure. 4.2. Forest structure dynamics 4.2.1. Forest composition and structure dynamics Analysis of changes in forest dynamics in 11 years on the PLs of the study area has obtained the results:
Table 0.8: Transformation of the composition in the study area 2007 2018 Plot HL Botanical composition HL Botanical composition 17,3 Castanopsis indica + 17,6 Castanopsis indica + 9,6 Garcinia fagraeoides 9,5 Garcinia fagraeoides + + 6,8 Hopea chinensis + 6,2 Diospyros sylvatica + HB01 1/9 1/8 5,8 Diospyros sylvatica, + 6,2 Hopea chinensis + 5,5 5,6 Manglietia dandyi + Garcinia oblongifolia + 54,9 others 55,0 others 21,8 Lithocarpus 20,1 Lithocarpus dealbatus dealbatus + 16,3 + 16,3 Castanopsis indica + Castanopsis indica + 11,6 HB03 1/10 1/11 10,1 Trema orientalis + 7,0 Trema orientalis + 7,8 Lithocarpus ducampii + Lithocarpus ducampii + 46,6 others 42,4 others 24,8 Diospyros sylvatica + 10,0 Lithocarpus 24,3 Diospyros sylvatica + dealbatus + 8,2 Garcinia 8,0 Lithocarpus dealbatus + HB06 1/7 fagraeoides + 7,3 Vatica 1/6 7,8 Garcinia fagraeoides + odorata ssp + 5,6 6,9 Vatica odorata ssp + 53 Lithocarpus ducampii + others 44,1 others 20,8 Saraca dives + 6,8 21,5 Saraca dives + 6,7 Aglaia lawii + 5,9 Aglaia lawii + 5,8 XS01 1/5 Pometia pinnata + 5,8 1/5 Barringtonia acutangula + Barringtonia acutangula 5,6 Pometia pinnata + 60,4 + 60,7 others others 9,2 Saraca dives + 6,9 8,9 Saraca dives + 6,7 Bhesa robusta + 6,5 Bhesa robusta + 6,7 XS02 1/4 1/4 Barringtonia acutangula Barringtonia acutangula + + 77,4 others 77,7 others 6,6 Nephelium 6,0 Nephelium cuspidatum cuspidatum + 5,7 Aglaia + 5,7 Wrightia tomentosa + XS03 1/5 1/5 argentea + 5,2 Wrightia 5,2 Aglaia argentea + 78,7 tomentosa + 82,5 others others Thus, the forest protection planning in Xuan Son National Park has little variation in species composition. In contrast, in the area of Hang Kia - Pa Co, forest protection areas have variation in species composition and other characteristics. In general, there is almost no change in dominant species between 2 times in the PL.
There is a tendency to gradually decrease the dominance of ecologically dominant species (the grouping coefficient decreases), there is an increase in dominance of other species not present in the formation. 4.2.2. Structure dynamics N/D1.3 Structure dynamics N/D1.3 of the study area have similarities. Trends in structural changes N/D1.3 are in two directions: the number of trees in the first diameter class decreases sharply, the number of trees in the first diameter class increases gradually. The process of structural transformation N/D1.3 also leads to the changes of other factors such as total cross section, average diameter, and status of the forest stand … 4.3. Additional regeneration, level change and death process in forest stand 4.3.1. Characteristics of additional regeneration, transition and death processes in the forest stand The dynamics of two areas, Xuan Son National Park and Hang Kia - Pa Co conservation area are fundamentally different. In Xuan Son National Park, the forest protection zones are in a relatively stable phase, the dynamic indicators have small changes, the density of stands is relatively low, the trees have large diameter on average. In contrast, in Hang Kia - Pa Co conservation area, the forest is in a period of strong development, there is a big change in forest structural factors. There is a greater variation in forest dynamics. 4.3.2. Simulate dynamics processes in the stand. 4.3.2.1. Simulate additional regeneration In the framework of this thesis, we have tested to explore the relationship between the number of additional regenerated trees and
the density, the relationship between the number of additional regenerated trees and the total cross section in the study area. The trial results in the area of Hang Kia - Pa Co and Xuan Son National Park show that: there is no suitable function to simulate the relationship between the number of additional regenerated trees and the density and total cross section of the stand. To estimate the number of additional regenerated trees, we can estimate from the relative ratio of the number of replenished trees to the stand density. 4.3.2.2. Simulate the transition process In Hang Kia Pa Co area, there are 2 different forest states (state IIIA3 and IV), so this process simulation is calculated for each state. Functional test results can best simulate the relationship between the number of transgenic trees and the diameter we get the results: Ok = -0,318 + 0,599 * Nk - 0,002* Nk2 + 4,971*10-6* Nk3 (4-2) With state IV, the quadratic function is selected to express the relationship between (Ok-Nk) by the equation: Ok = -0,374 + 0,388 * Nk -0,00046* Nk2 (4-3) Thus, in the area of Hang Kia - Pa Co, the number of transgenic trees depends closely on the number of trees at each diameter size in both state IIIA and state IV. The equation for simulating the relationship between the number of transgenic trees and the diameter classification at Xuan Son is as follows: Ok = 95,739 – 3,915* Dk + 0,054* Dk2 – 0,00025* Dk3 (4-5) In addition, this study also simulates the relationship between the transition ratio and the diameter class. However, the research
results show that this relationship exists, but the correlation coefficient R2
Ok = -0,374 + 0,388 * Nk -0,00046* Nk2 Number of dead trees at each diameter level simulated by function: Mk = -0,905 + 0,182 * Nk Figure 0.1: Diagram simulating forest structure dynamics After having these equations, we proceed to load the elements of the model into the simulation diagram. After completing the simulation diagram, we can export the model to a text file. The results of the model run reflect the dynamics of the system, which can be seen the changing trend of the elements over time, thereby giving an overview of the system dynamics. Research data is collected over 11-year period, time step is 1 corresponding to the change of forest in 11 years. For more details of these fluctuation process, we draw graphs to see those cycles in general. In short, with the use of MM&S software, we can quickly run the model and see how the factor levels change over time (here is the variation of each diameter class over time. time). However, to see the overall variation in levels of each factor over time (the variation of all diameter classes over time) we need to save the spreadsheet as a