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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]
(1)MINISTRY 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
Major: Ecology Code: 42 01 20
SUMMARY OF BIOLOGY DOCTORAL THESIS
(2)
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 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:
(3)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 (coverage reached 43%); however, by 1990 the forest area was severely reduced to 9.18 million (coverage reached 27.2%); in the years 1980 - 1990, on average, our country lost 100,000 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 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
(4)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 Study overview (30 pages)
Chapter Subject, scope, content limitation and study method (14 pages)
(5)Chapter 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 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
(6)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
(7)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:
(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 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
(9)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 CHARACTERISTICS OF THE STUDY AREA 3.1 Characteristics of natural conditions
3.1.1 Geographical location
(10)Located in the north of Mai Chau District, west of Hoa Binh Province, within the administrative boundaries of communes: Hang Kia, Pa Co, Tan Son, Bao La, Cun Pheo, and Pieng Ve with the total area of 7,091 ha, including subdivisions:
- Strictly protected subdivision: 2,680 - Ecological rehabilitation subdivision: 4,411 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 of forest land; and 118.1 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
(11)CHAPTER 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
1 HB01 67 608 1/9
17,3 Castanopsis indica + 9,6
Garcinia fagraeoides + 6,8 Hopea chinensis + 5,8 Diospyros sylvatica, + 5,6 Manglietia dandyi
+ 54,9 others
2 HB03 56 571 1/10
21,8 Lithocarpus dealbatus + 16,3
Castanopsis indica + 11,6 Trema orientalis + 7,8 Lithocarpus
ducampii + 42,4 others
3 HB06 70 466 1/7
24,8 Diospyros sylvatica + 10,0
Lithocarpus dealbatus + 8,2 Garcinia fagraeoides + 7,3 Vatica
odorata ssp + 5,6 Lithocarpus ducampii + 44,1 others
4 XS01 71 344 1/5
20,8 Saraca dives + 6,8 Aglaia
lawii + 5,9 Pometia pinnata + 5,8 Barringtonia acutangula + 60,7
others
5 XS02 86 352 1/4
9,2 Saraca dives + 6,9 Bhesa
robusta + 6,5 Barringtonia acutangula + 77,4 others
6 XS03 106 487 1/5
6,6 Nephelium cuspidatum + 5,7
(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 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
(13)Questioning: is the 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 HB01 67 608 1/9 3.31126 0.92541 HB03 56 571 1/10 2.68794 0.86451
(14)3 HB06 70 466 1/7 2.93660 0.88831 XS01 71 344 1/5 3.38190 0.92425 XS02 86 352 1/4 3.84813 0.96488 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:
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
0
0 0,25 0,5 vc
Rényi
(15)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 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 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 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
(16)Table 0.8: Transformation of the composition in the study area
Plot
2007 2018
HL Botanical composition HL Botanical composition
HB01 1/9
17,3 Castanopsis indica + 9,6 Garcinia fagraeoides
+ 6,8 Hopea chinensis + 5,8 Diospyros sylvatica, +
5,6 Manglietia dandyi + 54,9 others
1/8
17,6 Castanopsis indica + 9,5 Garcinia fagraeoides +
6,2 Diospyros sylvatica + 6,2 Hopea chinensis + 5,5
Garcinia oblongifolia +
55,0 others
HB03 1/10
21,8 Lithocarpus
dealbatus + 16,3 Castanopsis indica + 11,6
Trema orientalis + 7,8 Lithocarpus ducampii +
42,4 others
1/11
20,1 Lithocarpus dealbatus + 16,3 Castanopsis indica + 10,1 Trema orientalis + 7,0
Lithocarpus ducampii +
46,6 others
HB06 1/7
24,8 Diospyros sylvatica + 10,0 Lithocarpus
dealbatus + 8,2 Garcinia fagraeoides + 7,3 Vatica
odorata ssp + 5,6 Lithocarpus ducampii +
44,1 others
1/6
24,3 Diospyros sylvatica + 8,0 Lithocarpus dealbatus +
7,8 Garcinia fagraeoides + 6,9 Vatica odorata ssp + 53
others
XS01 1/5
20,8 Saraca dives + 6,8
Aglaia lawii + 5,9 Pometia pinnata + 5,8 Barringtonia acutangula
+ 60,7 others
1/5
21,5 Saraca dives + 6,7
Aglaia lawii + 5,8 Barringtonia acutangula +
5,6 Pometia pinnata + 60,4 others
XS02 1/4
9,2 Saraca dives + 6,9
Bhesa robusta + 6,5 Barringtonia acutangula
+ 77,4 others
1/4
8,9 Saraca dives + 6,7
Bhesa robusta + 6,7 Barringtonia acutangula +
77,7 others
XS03 1/5
6,6 Nephelium
cuspidatum + 5,7 Aglaia argentea + 5,2 Wrightia tomentosa + 82,5 others
1/5
6,0 Nephelium cuspidatum + 5,7 Wrightia tomentosa +
5,2 Aglaia argentea + 78,7 others
(17)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
(18)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 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:
(19)results show that this relationship exists, but the correlation coefficient R2 <0.4, so not simulate this relationship (App 5.3) 4.3.2.3 Simulate the process of death in the stand
The test results showed that no relationship between the number of dead trees, the mortality rate and the density and cross section of the stand was found The experiment studies the relationship between the number of dead trees and the diameter class (Mk-Dk) for the IIIA3 state, the results: the equation used to simulate the relationship between the number of dead trees at each diameter level shows that class linear function is chosen for simulation with the following equation:
Mk = 0,236 + 0,126 * Nk (4-7) For state IV:
Mk = -0,905 + 0,182 * Nk (4-8)
Similar test results for Xuan Son area show that there exists a relationship between Mk – Dk: The inverse function is best suited to describe the relationship between the number of dead trees in diameter classes:
Mk = -2,279 + 153,338/Dk (4-11) 4.4 Recommended research result application
4.4.1 Forest structure simulation by using MM&S software Data collected in 2007 - 2018 on PL HB06 in Hang Kia - Pa Co Nature Reserve (NR) is used for modeling and simulation In order to conduct forest structure dynamics simulation, we first need to identify the elements of the system Using the correlation equation between the factors found in the previous section, as Fig 4.28
(20)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 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
(21)text file or a file excel On that basis, it is possible to draw the chart of changes of all factor levels in each period On the other hand, when using MM&S software, it is required to have a basic understanding of the system, about the system variables as well as the manipulation of this software In order to simplify the simulation of structural dynamics, we can use manual calculation method by using allometric equations between investigating factors which have been detected with the help of Microsoft Excel, details as below 4.4.2 Using the identified equations to simulate the structural dynamics of the stand
The tree death rate model is built on the basis of observed data from the positioning plot in a certain technique and simulated by the general function of: M=f(G,N)
The additional regeneration model is simulated with the general function is R=f(G,N)
The diameter transformation and structural change of the forest were calculated using the formula (2-11):
Nk,t+1 = Nk,t + Rk – Ok – Mk
The test calculates the dynamic processes for state IV in Hang Kia - Pa Co The equations used for the calculation are as follows:
- Additional regeneration process: 13,5%*N0 (state IV) - The number of transgenic trees is determined by the formula: Ok = -0,374 + 0,388 * Nk -0,00046* Nk2
- The number of dead trees is determined by the formula: Mk = -0,905 + 0,182 * Nk
(22)Table 0.3: Predict the structure of the state IV stand in the future in Hang Kia - Pa Co
A B C D E F G H I J K L M N O P Q
1 D1.3 (cm)
2 From 10 15 20 25 30 35 40 45 50 55 60 65 70 75 Sum
3 To 15 20 25 30 35 40 45 50 55 60 65 70 75 80
4 D1.3(Avr) 12,5 17,5 22,5 27,5 32,5 37,5 42,5 47,5 52,5 57,5 62,5 67,5 72,5 77,5
5 Ok 44 28 22 20 10 2 2
6 Mk 24 14 10 0 0
7 N (trees/ha)
8 2018 135 82 62 56 27 16 24 17 6 11 457
9 2029 129 83 58 49 33 18 18 17 10 7 448
10 2040 125 82 57 44 33 21 15 15 12 7 440
11 G (m2/ha)
12 2018 1,66 1,97 2,46 3,32 2,24 1,77 3,40 3,01 1,30 1,56 3,37 1,43 2,06 2,83 32,39
13 2029 1,59 2,00 2,31 2,89 2,75 1,99 2,49 3,08 2,16 1,51 2,45 2,45 1,90 3,47 33,04
(23)4.5 Solution proposal for forest management 4.5.1 Recommended patterns
The thesis has selected three orientations for N/D1.3 for the research stands corresponding to each state Criteria to choose, propose orientation patterns include:
1 The species composition is diverse, including dominant indigenous tree species
2 Total cross-section and reserves is high
3 There is N/D distribution according to the reduced distribution, well simulated by the distance distribution Characteristics of the sample stand are common
These orientational patterns are the basis for the application of silvicultural measures in the process of tending and nurturing forests 4.5.2 Proposing some forest management measures in the study area
Based on the research results, the topic proposes some forest management measures as follows:
- Technical solution for structural regulation: is an impact technical solution to lead the current forest to achieve a oriented forest structure
+ For the stands that have reached the desired threshold, need to maintain a stable state, forest zoning and protection should be conducted Avoid negative impacts on forests
(24)With different forest states, the applied silviculture techniques need to be suitable with the characteristics of that forest condition On the basis of the study, the topic proposes a number of silvicultural measures for specific forest objects
CONCLUSIONS AND RECOMMENDATIONS 1 Conclude
1.1 Regarding forest structure characteristics
The number of species in the study area varied from 56 to 106 species The number of species that dominate clearly in PLs ranges from 3-5 species Plant composition was significantly different between plots and between study areas
The distribution N/D1.3 has a reduced form The largest number of trees are concentrated in the first and second diameter classes The mean diameter at Hang Kia - Pa Co is lower than that in Xuan Son The distance function is suitable for describing the distribution of trees by diameter classes
Distribution N/Hvn has the form of a curve with many vertices, heterogeneous among the study plots All three distribution functions are not suitable to describe the N/Hvn distribution in Hang Kia - Pa Co The Weilbul function is suitable to describe this distribution in the Xuan Son area
1.2 Regarding structural dynamics
(25)Kia - Pa Co there is substitution of dominant species in the formula of forest composition
The variation in the number of trees by diameter class in the PLs was different but not significant, with the largest concentration of trees at the diameter class from 10 cm to 20 cm The natural death rate is highest at the smallest diameter classes
1.3 Regarding additional regeneration dynamics, transition and mortality: The number of dead trees in the Hang Kia - Pa Co area was 222, with an average of 20 dead trees per year in the entire study area (about trees/ha/year) The corresponding death rate is about 9.7% In Xuan Son National Park, the number of dead trees is only 90 trees, averaging 2.7 trees/ha/year The corresponding mortality rate is about 7.5%
The rate of additional regeneration in Hang Kia - Pa Co is about 15.5% (equivalent to 1.4%/year) and in Xuan Son is 12% (equivalent to 1.1%/year) There is a difference in the gradation rate between different diameters and PL objects
No relationship exists between the number of regenerated trees and other factors A relationship exists between the number of transgenic trees, the number of dead trees and the diameter class, and the number of trees per diameter class
The suitable equations for simulating the dynamics: - State IIIA3: Mk = 0,236 + 0,126 * Nk
Ok = -0,318 + 0,599 * Nk - 0,002* Nk2 + 4,971*10-6* Nk3
- State IV: Ok = -0,374 + 0,388 * Nk -0,00046* Nk2
M
(26)Ok = 95,739 – 3,915* Dk + 0,054* Dk2 – 0,00025* Dk3 1.4 Recommended research result application
Use MM&S software and found equations to simulate the structural dynamics of the forest
1.5 Solution proposal for forest management
The study of structural dynamics is the basis for proposing impact measures aimed at guiding the forest according to the directional patterns Based on the actual dynamic indicators, based on the found correlation equations, it is possible to predict the structure of the stand in the future, serving the sustainable management of forest resources On that basis, some solutions for sustainable forest management were proposed
2 Existing limitation
- Similar studies have not been performed in many different locations
- Research on positioning PL (PLDV) with a period of 11 years, so it is possible that the dynamics cycles are not clearly shown
3 Recommendation
- Continuing to monitor on the positioning PLs in the coming years to more accurately identify the results of the dynamics processes
(27)NEW CONTRIBUTIONS OF THE THESIS
1 The dynamics and characteristic structure of forest tree communities have been identified in Hang Kia - Pa Co Nature Reserve and Xuan Son National Park
2 Identified a number of mathematical equations to simulate the dynamics of canopy layer structure and predict the forest structure in the future
3 The change in regeneration tree class, especially the number of dead trees and the number of trees added to the canopy layer has been identified in tree communities in Hang Kia - Pa Co Nature Reserve and Xuan Son National Park
LIST OF PUBLISHED SCIENTIFIC PAPERS
1 Nguyen Tien Dung, “Structural and dynamic properties of natural forest in Hang Kia - conservation reserve”, Vietnam Journal of Forest Science, 2013, No 4/2013
2 Nguyen Tien Dung, “Simulate dynamic nature forest stand in Xuan Son National Park, Phu Tho Province”, Science and Technology Journal of Agriculture & Rural Development, 2014, No 05/2014 (236)
3 Nguyen Tien Dung, Tran Van Con, “Structure of forest and species diversity in Hang Kia – Pa Co Natural Reserve”, Science and Technology Journal of Agriculture & Rural Development, 2014, No 06/2014 (237)
4 Nguyen Tien Dung, “Visualization and simulation of structural dynamics of natural broad-leaved evergreen forest at Xuan Son national park”, Academia Journal of Biology, 2018 Vol 40, No 4 (2018)