The growth and quality of indigenous tree species planted under the forest canopy in thach thanh district thanh hoa province

ABSTRACT The purpose of this research is studying on growth characteristics and quality of indigenous tree species planted under the canopy of Acacia auriculiformis plantations.. While

MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT VIETNAM NATIONAL UNIVERSITY OF FORESTRY

STUDENT THESIS

THE GROWTH AND QUALITY OF INDIGENOUS TREE SPECIES PLANTED UNDER THE FOREST CANOPY IN THACH THANH

DISTRICT, THANH HOA PROVINCE

Major: Natural Resources Management Faculty: Forest Resources and Environmental Management

Student: Nguyen Ngoc Khanh Student ID: 135 309 1001 Class: K59B - Natural Resources Management Course: 2014 - 2019

Advanced Education Program Developed in collaboration with Colorado State University, USA

Supervisor: Assoc.Prof Dr Pham Minh Toai

Ha Noi, October/2018

CONTENTS

LIST OF TABLES

LIST OF FIGURES

LIST OF ABBREVIATIONS

ACKNOWLEDGEMENT

ABSTRACT

INTRODUCTION 1

CHAPTER 1: OVERVIEW OF RESEARCH 2

1.1 In the world 2

1.1.1 Research on mixed plantations 2

1.1.2 Research on indigenous trees planting under forest canopy 3

1.2 In Viet nam 4

1.2.1 Research on mixed plantations 4

1.2.2 Research on indigenous trees planting under forest canopy 6

1.3 Techniques for planting indigenous forests under the forest canopy of the project 9

1.3.1 History of forest plantation in the research area 9

1.3.2 Techniques for planting Acacia auriculiformis forests of the project 10

1.3.3 Technique for planting indigenous forest under forest canopy 10

1.3.3.1 Technical procedures for planting Erythrophleum fordii based on the project regulations (2011) 10

1.3.3.2 Technical procedures for planting Hopea odorata based on the project regulations (2011) 11

CHAPTER 2: OBJECTIVES, CONTENTS AND RESEARCH METHODS 12

2.1 Objectives of the research 12

2.2 Subjects and research methods 12

2.2.1 Research methodology on standard plot 12

2.2.2 Research on the physical characteristics of soil in the research area 12

2.2.3 Research on the structure of forest 13

2.2.4 Methods of data processing 14

CHAPTER 3: NATURAL CONDITIONS OF RESEARCH AREA 16

3.1 Geographical location 16

3.2 Topographic 16

3.3 Hydrological conditions 17

3.4 Soil 17

3.5 Water resources 18

3.6 Forest resources 18

CHAPTER 4: RESULTS AND DISCUSSION 19

4.1 Growth characteristics and quality of indigenous trees under forest canopy in the study area 19

4.1.1 Growth characteristics and quality of Erythrophleum fordii 19

4.1.1.1 Growth characteristics of Erythrophleum fordii 19

4.1.1.2 The quality of growth of Erythrophleum fordii 22

4.1.2 Growth characteristics and quality of Hopea odorata 23

4.1.2.1 Growth characteristics of Hopea odorata 23

4.1.2.2 The growth quality of Hopea odorata 27

4.2 Evaluate the factors affecting the growth of indigenous plants 28

4.2.1 Factors affecting the growth of Erythrophleum fordii 28

4.2.1.1 The structure and growth of tall plant of Acacia auriculiformis 28

4.2.1.2 Characteristics of soil under forest canopy 30

4.2.2 Factors that affect the growth of Hopea odorata 31

4.2.2.1 The structure and tall plant growth of Acacia auriculiformis 31

4.2.2.2 Characteristics of soil under forest canopy 32

4.3 Proposing some silvicultural techniques to promote the growth of indigenous trees in the research area 33

4.3.1 Impact solution in Erythrophleum fordii forest 34

4.3.2 Impact solution in the Hopea odorata forest 34

CHAPTER 5: CONCLUSION, CONSTRAINTS AND RECOMMENDATIONS 35

5.1 Conclusion 35

5.2 Constraints 35

5.3 Recommendations 36 REFERENCES

APPENDIX

LIST OF TABLES

Table 2.1: Forest land profile analyzing results 12

Table 2.2: Growth characteristics of Acacia auriculiformis 13

Table 2.3: Growth Characteristics of indigenous trees 14

Table 4.1: Growth Characteristics of Erythrophleum fordii (7 years) 19

Table 4.2: Comparison of the difference in diameter at breast height (D1.3) of Erythrophleum fordii between standard plots (U standard) 19

Table 4.3: Comparison of the difference in the total height (Ht) of Erythrophleum fordii between standard plots (U standard) 20

Table 4.4: Comparison of the difference in diameter of the canopy (Dc) of Erythrophleum fordii between standard plots (U standard) 21

Table 4.5: Percentage of good, medium and bad trees of Erythrophleum fordii forest 22

Table 4.6: Growth Characteristics of Hopea odorata (7 years) 23

Table 4.7: Comparison of the difference in diameter at breast height (D1.3) of Hopea odorata between standard plots (U standard) 23

Table 4.8: Comparison of the difference in the total height (Ht) of Hopea odorata between standard plots (U standard) 24

Table 4.9: Comparison of the difference in diameter of the canopy (Dc) of Erythrophleum fordii between standard plots (U standard) 25

Table 4.10: Percentage of good, medium and bad trees of Hopea odorata forests are summarized in the table: 28

Table 4.12: Distribution of growth quality of Acacia auriculiformis forest (Erythrophleum fordii under canopy) 29

Table 4.13: Erythrophleum fordii forest land profile analyzing results 30

Table 4.14: Growth characteristics of Acacia auriculiformis (Hopea odorata under canopy) (11 years) 31

Table 4.15: Distribution of growth quality of Acacia auriculiformis forest (Hopea odorata under canopy) 32

Table 4.16: Hopea odorata forest land profile analyzing results 33

LIST OF FIGURES

Figure 4.1: Comparison of diameter at breast height (D1.3) of Erythrophleum fordii under

canopy of Acacia auriculiformis 20

Figure 4.2: Comparison of the total height (Ht) of Erythrophleum fordii under canopy of

Acacia auriculiformis 21

Figure 4.3: Comparison of diameter of the canopy (Dc) of Erythrophleum fordii under

canopy of Acacia auriculiformis 22

Figure 4.4: Comparison of diameter at breast height (D1.3) of Hopea odorata under canopy

of Acacia auriculiformis 24

Figure 4.5: Comparison of the total height (Ht) of Hopea odorata under canopy of Acacia

auriculiformis 25

Figure 4.6: Comparison of diameter of the canopy (Dc) of Erythrophleum fordii under

canopy of Acacia auriculiformis 27 Picture 4.2: Soil profile in Hopea odorata area 33

LIST OF ABBREVIATIONS

SP Standard plot

D1.3 Diameter at breast height (m)

HT The total height (m)

HUC The height under canopy (m)

DC Diameter of the canopy (m)

̅1.3 The average of diameter at breast height (m)

̅t The average of total height (m)

̅c The average of diameter of the canopy (m)

CC Canopy cover

JICA Japan International Cooperation Agency

KfW German Reconstruction Banks

ACKNOWLEDGEMENT

This thesis was completed at the Vietnam National University of Forestry, following the undergraduate training programs in the period of 2014-2019 with the natural resources management major (Advanced Education Program) This major was developed

in collaboration with Colorado State University, USA During the implementation and completion of the thesis, the author has received the support from School-Board of University, Faculty of Silviculture, Faculty of Forestry and Environmental Management that was precious and effective

The author expresses the sincere and deepest gratitude to Assoc Prof Dr Pham Minh Toai as an instructor who has paid attention to the thesis, spent a lot of time for instruction and provided many relevant valuable materials These have helped the author to complete this thesis

The author would like to thank the leaders and officers of the Management Board for Forestry Projects to facilitate the study and completion of the thesis

Finally, the author would like to express sincere gratitude to friends, classmates, and supporters during the studying years as well as the completion of this thesis

Sincerely thanks!

Hanoi, October 30th, 2018 Student

Nguyen Ngoc Khanh

ABSTRACT

The purpose of this research is studying on growth characteristics and quality of indigenous tree species planted under the canopy of Acacia auriculiformis plantations The thesis has clarified the stand’s structure and quality of indigenous tree species, characteristics of soil under the forest canopy and the effects of tall trees to indigenous trees, then has provided silvicultural solutions The research will help to improve the

growth of indigenous trees in the next years

INTRODUCTION

In recent years, the trend to develop indigenous tree species has become stronger and can achieve many objectives in terms of economic, social and environmental aspects However, the indigenous plantation programs/projects have still faced many difficulties due

to the lack of support from managers, investors and forest owners

The afforestation project implemented in Thanh Hoa and Nghe An provinces (KfW4)

is one of the forestry programs focusing on the development of indigenous tree species,

mainly such as Erythrophleum fordii, Peltophorum pterocarpum, Hopea odorata,

Mylopharyngodon piceus, Michelia mediocris Dandy, etc with the target of developing

19,000 ha of sustainable production forest for over 14,000 households in 53 communes of 10 mountainous districts of two project provinces

The development of indigenous tree species is carried out with two forest types: 1) Planting pure indigenous trees; 2) Planting indigenous trees under the Acacia auriculiformis

canopy The area of 3,000 ha of planted pure indigenous tree species (mainly Aquilaria

crassna, Chukrasia tabularis, etc.) has become forest and has been initially evaluated to be

well-grown While the area of about 300 ha of indigenous tree species has been planted under

the forest canopy such as Erythrophleum fordii, Peltophorum pterocarpum, Hopea odorata as

a pilot in Thach Thanh, Cam Thuy and Vinh Loc districts (Thanh Hoa province) and in Quynh Luu and Yen Thanh districts (Nghe An province)

Within the scope of KfW4 plantation area, factors such as site conditions, seedlings, and climatic conditions are almost identical but canopy cover is the most important factor affecting the growth of indigenous tree species planted under the forest canopy Generally, most indigenous species are well-grown in shade-tolerant conditions at an early age, but their light needs will change over time

Therefore, the assessment of affect of canopy cover during each specific development stage of indigenous trees is practical as a basis for proposing appropriate measures to promote the growth of indigenous tree species under forest canopy With the above reason, the project

on "The growth and quality of indigenous tree species planted under the forest canopy in

Thach Thanh district, Thanh Hoa province" is necessary, contributing to construction of

theoretical and practical basis to develop the indigenous plantations in the coming project phases

CHAPTER 1: LITERATURE REVIEWS 1.1 In the world

1.1.1 Research on mixed plantations

Researches in many countries around the world show that pure plantations have shown many disadvantages Therefore, scientists in the world have been interested in studying the development of mixed forest models for sustainable forest business, especially in the current phase of climate change

In Malaysia (1999) [19], the multi-layered forestation project has introduced a model

of mixed plantation on three species: natural forest, 10-15 year Acacia plantation and 2 - 3 year Acacia plantation The project uses 23 valuable indigenous species by planting strips in natural forest, each strip includes three rows of indigenous trees Total of 14 indigenous

species planted under the Acacia mangium canopy is divided into two experimental blocks:

Block A: Open the10m strip, plant 3 rows of indigenous trees

Open the 20m strip, plant 7 rows of indigenous trees

Open the 40m strip, plant 15 rows of indigenous trees

Block B: Cut a row of acacia, plant a row of indigenous trees

Cut 2 rows, plant 2 rows of indigenous trees

Cut 4 rows, plant 4 rows of indigenous trees

The results show that three species among 14 species of Block A have the fastest

tree-height growth and the best diameter growth, including Shorea roxburrghii, Shorea ovalis and

Shorea leprosula The tree-height growth of indigenous tree species planted in the 10m and

40m strips is better than those planted in the 20m strip The best tree-height growth is shown

in the formula of mixed planting of one Acacia row and one indigenous row From this studying result, some recommendations to adjust the growth of experimental models at eight times of 2-8-12-18-28-34-41-47 years after planting are given This is one of research projects

on the of mixed-species forest establishment that is relatively complete in terms of technical measures, from the selection of tree species to study of planting method, timing of planting and model adjustment following the growing process for a long time Therefore, these pilot models will have many promising successes in future and can be replicated in practice

The outstanding feature of mixed plantations is the multi-layered canopy Therefore, many global scientists have been interested in the establishment of multi-layered plantations During the study of canopy structure of mixed stands, Bernard Dupuy (1995) [20] has shown that the canopy structure of mixed plantations depends on the growth and solidarity of tree species in stands This shows that the mixed plantation models having reasonable structure and taking full advantage of nutrient space in maximum are only established once we base on

ecological characteristics as well as pay attention to interrelationships between tree species to select the appropriate tree species These are important bases to determine the success or failure of mixed plantation models

1.1.2 Research on planting indigenous tree species under the forest canopy

In recent years, the indigenous tree species have been studied, experimentally and successfully planted in many places over the world Of which, many trees belonging to

Paulownia genus have been paid attention by many regional and global countries According

to Tran Quang Viet (2001) [1], from the 1960s in China, along with the forestation movement and construction of protection forest belts, the Paulownia tree species were further researched and developed by the Chinese Academy of Forestry (CAF); CAF has conducted a systematic study of classification, ecological characteristics, distribution, planting techniques and

utilization of Paulownia tree species

Basically, some other studies - such as planting on the strip and underplanting in African and Asian countries - are also to establish the mixed forest stands on the basis of existing tree species In the areas where the Important Value of economically valuable tree species is low, the forest quality can be improved by increasing the quantity of tree species and quantity of individuals of economically valuable species through enrichment planting, for examples: planting in Nigeria, Congo, Cameroon, etc These studies have achieved many good results through taking advantage of natural cover which has supported the main crops at the early stages The Potential Crop Trees (PCTs) for supplementary planting still live in the moist forest On the other hand, when the plants grow up, the opening of canopy of upper tree species has been adjusted in time The removal of vines and shrubs was also carried out regularly, so the PCTs for supplementary planting were well-grown, forming high-yielding mixed forest stands This is an important lesson in selection of supporting trees for the research project on technical measures of mixed forest of broad-leaved species

In order to effectively manage the forest, each species needs to have its own density and thinning for growing and developing E.Assman (1961) [21], after reviewing 9 thinning models with 4 tree species, indicated that thinning could not increase total timber output of

forest stands However, with the Picea forest stands, intensively thinning will increase the tree

volume to 15-20% compared to trees without thinning In comparison with the tree diameter

growth in the Tectona grandis forest stand at the age of 26 which was intensively thinned at

age 14 Iyppu and Chandrasekharan (1961) [23], it was found that the tree diameter in the stands with intensively thinning was 39.9 cm while the diameter in the stands without thinning was 29.5 cm In general, the authors conclude that when the density of forest stands decreases, the growth of individual trees, especially the diameter growth will increase sharply

while the total growth of forest stand will decrease, not increase or increase very little The increase in total yield by thinning is only due to the amount of products removed from thinning

The effect of planting density on the canopy development is quite obvious The study

of Pinus patula, Julians Evan [18] shown that in the 19-year-old forest without thinning, the

length of canopy was only 29% of total length of the trunk; while at this age, in the forest that was thinned once at the age 9, the canopy length was up to 40% of stem length For canopy

area, Hunt (1969) [24] compared the effect of thinning to the 22-year-old forest stand of Pinus

strobus and concluded that after 5 years of thinning, total leaf weight of the forest after

thinning was 3 times higher than total leaf weight of forest stand without thinning

Research the differences in sparse of trees in forest stand with different densities Van

laar (1976) [25], showed that with Pinus planted in South Africa, in the stands with high

density (3000 trees/ha) the tree value was 0.565; whereas in the stands with low density (125 trees/ha), the same numerical value was only 0.495

The above research shows that there is a real relationship between the morphological parameters/ quality of forest trees and the densities These are important conclusions not only

on theoretical implications but also on silvicultural significance However, the above results are only qualitative or quantitative comparisons Therefore, the research on finding relationships modeled mathematically between ecological factors, tree quality and density is very necessary, in which the density can be expressed in many other ways

1.2 In Viet Nam

1.2.1 Research on mixed plantations

Nguyen Ba Chat (1995) [17], when researching the forest restoration in Song Hieu (1981 - 1985), experimented with planting Chukrasia tabularis mixed with other indigenous species such as Peltophorum pterocarpum, Michelia mediocris Dandy, Gmelina arborea Roxb, etc to create a reasonable structure After 10 years, the results showed that the mixed planting

of Chukrasia tabularis is better than the pure planting of Chukrasia tabularis Mixed forest using natural vegetation has better advantages on growth of tree species and has shown signs

of better soil recovery

Tran Ngu Phuong (2000) [3] has also studied on establishing the mixed plantation models to create multi-layer forest canopy for protection and production through the variously mixed plantations such as mixture of tall trees and shrubs, mixture of tall trees and tall trees Based on the studying results of main laws of natural forest in northern Vietnam, the author has shown that forest vegetation in our country is divided into many layers, from 2-3 timber tree layers, not including the medium tree layer and fresh vegetation Based on this principle,

the author has proposed a model of afforestation to meet the objectives of watershed protection in key areas, of which two outstanding models of mixed afforestation are a mixed model of permanent multi-layer production forest and a mixed model of temporary secondary multi-layer production forests

Pham Xuan Hoan (2004) [5] experimented on mixed plantation at Vietnam university,

planted 165 indigenous species under the canopy of Pinaceae and Acacia, of which 27 indigenous species planted under the Pinus massoniana canopy, 21 indigenous species planted under the Acacia auriculiformis canopy, the remaining planted under the mixed forest canopy between Pinus massoniana and Acacia auriculiformis, Pinus massoniana and Acacia

mangium, Eucalyptus, etc The survival rate of indigenous species under the Pine canopy and

under the Acacia canopy was estimated to respectively reach 93.2% and 91.2% The regular

growth and average growth of indigenous species vary widely among species Especially,

some species - which have been often evaluated to have slow growth such as Cinnamomum

parthenoxylon, Erythrophleum fordii, etc but have good shade tolerance at the early stages

under the Pine and Acacia canopies - were well-growth and very promising

National Program 327 (a program of greening barren hills was implemented from

1993 to 1998) and the 661 projects (5 million hectares of newly planted forests, inherited from Program 327) have also established many mixed plantations with indigenous broadleaf species, mainly established protection forests in the key areas nationwide Most of these

models use the supporting species such as Acacia mangium, Acacia auriculiformis, Senna

siamea with the mixed rate of 600 indigenous trees and 1000 supporting trees/ha However,

the adjustment of canopy of supporting species in the mixed forest models has not been paid attention and adjusted in time, so the main species have the very low survival rate and often grow poorly This is also a common weakness of most models in Project 327 and 661

In addition to the research on establishment of mixed plantations by broadleaf species, there are several research projects that create the mixed plantations between coniferous species and broadleaf species, among imported species Phung Ngoc Lan (1986) [7] studied the experiment of creating the mixed forests in Luot Mountain - Vietnam National University

of Forestry - Xuan Mai, Pinus massoniana is selected as the main species The author studied the mixed plantation of Pinus massoniana, Acacia auriculiformis and Eucalyptus

camaldulensis in the different proportions, density, method and timing Based on the criteria

of growth, soil and diseases, the authors made the following remarks:

+ After 2 years of growth, the mixed plantation of Pinus massoniana was better than the pure plantation of Pinus massoniana The mixed ratio has no significant effect on the growth of Pinus on the test formulas

+ In the mixed plantation formulas that were conducted, the earthworm efficiency was more developed than the pure plantation formulas This suggested that the soil properties were improved significantly in the mixed plantations

After 2 years, the authors found that the height growth of pure Pinus plantation was 2.53 m, while the height of Pinus mixed Acacia plantations with the ratio 1: 1 and the scale

1:2 respectively was 2.8 m and 2.72 m The diameter growth of Pinus mixed Acacia plantations with the ratio 2: 1 ratio was also greater and faster In the mixed plantation of Pinus massoniana and Eucalyptus camaldulensis, the Pinus growth was unknown

1.2.2 Research on planting the indigenous trees under the forest canopy

In our country, the selection of indigenous species having advantages such as rapid growth, good protection ability has a practical significance and scientific basis In the recent years, there have been many authors researching the conservation and development of some

indigenous species in Vietnam

Trieu Van Hung (1993), [6], studied the "Biological characteristics of some forest

enrichment plants (Canarium album, Peltophorum pterocarpum) According to his comment,

in the Important Value of natural forest, Canarium album achieved only 3.87% an average quantity of trees and 6.84% of standard plots The ratio of Canarium album in the forest status

of IIIA1 was higher than in the forest status of IIIA2 In the forest, Canarium album species often mixed with some other species such as Machilus bonii Lecomte, Peltophorum

pterocarpum, Choerospondias axillaris etc

Nguyen Hoang Nghia (1997) [9] introduced basic paradoxes of indigenous species, which highlighted the difficulties in planting the indigenous tree species in our country Phung Ngoc Lan (1994) [8], after studying the characteristics of Erythrophleum fordii,

confirmed: The distribution of Erythrophleum fordii was very large and could be found in

most of the northern provinces of Vietnam (from Hai Van onwards) with the altitude of 900m

or less in the south and 500 m or less in the north; developed in low mountains, slopes less than 20 degrees or in the foothills

Pham Xuan Hoan (2002) [4], from the study "Characteristics of some circumstantial factors of experimental mixed plantations of tropical broadleaf trees at Ecological Restoration Zone of Cat Ba National Park" and "Experimental research - planting indigenous trees under

the canopy of Pinus massoniana and Acacia auriculiformis in the experimental forest of

Vietnam National University of Forestry" The authors provided some results such as the good growth of some indigenous species planted under forest canopy, especially under the

canopy of Acacia auriculiformis and Pinus massoniana; and also identified some major

factors affecting the growth of indigenous species such as canopy cover of upper layers, light intensity, soil

According to Vi Hong Khanh (2003) [12], when assessing the growth of some indigenous species for forest conservation and development in Cau Hai - Phu Tho province, concluded that most Erythrophleum fordii had high survival rates and good growth; at the same time, out of 34 indigenous species, the study site selected the following tree species for

growth assessment: Cinnamomum bejolghota, Canarium album, Peltophorum pterocarpum,

Erythrophleum fordii, Prunus arborea, Michelia mediocris Dandy which were fast-growing,

well-adapted, resistant to pests and diseases and were capable of replication and development for similar site conditions

Vietnamese Academy of Forest Sciences - Japan International Cooperation Agency (2000) [13] - in the workshop on enhancing forest plantation in Vietnam with the collaboration of the Ministry of Forestry, the project on “Strengthening Re-afforestation Programmes in Vietnam” (STRAP) and Japan International Cooperation Agency (JICA) in

1994 made the important recommendation that more information on indigenous species should be available for local people to refer and find suitable tree species for afforestation In order to answer the above requirements, the STRAP project together with Vietnamese Academy of Forest Sciences implemented a project "Identifying high-quality indigenous tree species for afforestation in Vietnam" The results provided systematic and comprehensive information on 210 species of high-quality wood used for house building and high-end furniture Thereby, the potential of indigenous species in each region in the country is abundant However, the quantity of trees planted under the correct technique/model and suitable for plantation capacity was too little Therefore, it is important to study the remaining trees to change the potential into reality In addition, it is necessary to focus on research and development of high-value tree species to create the key plants for each region and for the whole country

Over many years of research, Vietnamese Academy of Forest Sciences has proposed over 100 indigenous tree species for afforestation programs for all three types of production forest, protection forest and special-use forests Based on the available literature and new data, 31 species of indigenous tree species were selected and reported for each species The indigenous tree species are evaluated in three levels:

- Species has been put into production, the forest area is up to thousands of hectares or at least a few hundred hectares, there are enough technical guiding procedures such as

Dipterocarpus alatus, Senna siamea, Pinus massoniana, Manglietia conifera,

- Species have been put into production on a small scale, but the models of planting are

big enough for evaluation such as Chukrasia tabularis, Michelia mediocris Dandy,

Peltophorum pterocarpum,

- Species that have been studied and experimented with small models such as Machilus

bonii Lecomte, Erythrophleum fordii,

Dao Cong Khanh (2003) [15], many species of pure plantations in Vietnam have been studied to transform into the mixed plantations with a more stable and sustainable structure by planting a number of Potential Crop Trees (PCTs) at different times Typically, the

"Afforestation in Bac Giang and Lang Son - KfW1" co-funded by the Government of the Federal Republic of Germany was implemented since 1995 Initially, the plantations in these

provinces included the pure Pinus massoniana or pure Acacia mangium plantations After 7

years of implementation, the project has been experimentally transformed into the mixed

plantations (Pinus or Acacia mixed with some other indigenous broadleaf species) by cutting

Pinus and Acacia, opening 3 m-wide strips and then planting indigenous broadleaf species in

the middle of two Pinus massoniana and Acacia mangium rows Thus, in considering the time

of mixed species, this can be considered as one of the typical and practical experiments because most plantations of our country are now pure plantations which needs to be transformed into a mixed plantations in order to make business in the more stable and sustainable ways

The RENFODA project (Rehabilitation of Natural Forest in Degraded Watershed Area

in the North of Vietnam) funded by JICA has studied the technical measures to rehabilitate the degraded natural forest in Cao Phong - Hoa Binh by establishing the mixed indigenous broad-leaved plantations (mixture of light-demanding and shade tolerant tall trees) The indigenous broad-leaved species were combined to produce the mixed plantations, including

Canarium album, Erythrophleum fordii and Lithocarpus ducampii The planting method is

mixture by group and by strip After 4 years of experiment (2004 - 2007), the showed that the tree species were very promising, the survival rate of all species was over 95% The growth of tree species planted by strip was better than species planted by group

Nguyen Duc The (2007) [14], wrote the project of mixed planting of high-value timber species that was collaborated between Research Institute of pulp and paper raw material tree species and the University of Queensland to supply timber and intensify the transaction between Vietnam and Australia (2002-2006) The project established the mixed plantations of exotic and indigenous tree species at the different timing in three sites:

 Doan Hung - Phu Tho: mixed planting of Eucalyptus, Chukrasia tabularis,

Canarium album, and Michelia mediocris Dandy at the same time

 National Park Tam Dao: mixed planting of Dracontomelon duperreanum, Khaya

senegalensis, Erythrophleum fordii with Acacia hybrid at the same time

 Hai Van Pass - Hue: mixed species of Acacia auriculiformis and Hopea odorata,

Dipterocarpus alatus, Parashorea chinensis (Acacia auriculiformis was planted 7 years ago,

then cut into strips to plant native species under the Acacia canopy with a density of 250 trees/ha)

After 3 years of implementation, the result showed that all tree species had a high survival rate, good growth, and good prospects However, this was only the initial result On the other hand, when designing the model, researching the relationship of tree species was not focused on Therefore, it should monitor this model to have intervention to timely regulate the

competition among species, especially fast-growing species such as Eucalyptus and Acacia,

facilitating the well-grown indigenous tree species

In conclusion, the research of growth of indigenous trees planted under the forest canopy is considered as a basis for selecting indigenous species, method of mixed planting, adjusting the canopy cover of upper layers which are suitable for the indigenous species growth to improve quality of forest plantation - it is a right orientation, has a scientific basis and the ability to apply in practice Therefore, the study of growth of indigenous species under

canopy, especially under the Acacia auriculiformis canopy in the KfW4 project, is essential

for developing the indigenous tree species under the canopy in the next stage in particular and contributing to planting indigenous tree species under the canopy in Vietnam in general

1.3 Techniques for planting indigenous forests under the canopy in the KfW4 project 1.3.1 History of plantations in the research area

The project “Afforestation in Thanh Hoa and Nghe An provinces” was implemented in

53 communes of 10 districts of Thanh Hoa and Nghe An provinces with the goal of establishing 19,000 hectares of sustainable forest

Over a period of 10 years of project implementation from 2002 to 2012, the whole project has set up 19,685 hectares of forest (of which the area of indigenous trees is 6,400 hectares; 4,200 hectares of fast-growing trees; the rest is regeneration trees with 9,085 hectares) The area of indigenous trees planted under forest canopy is 367.369 hectares

including species: Erythrophleum fordii, Michelia mediocris Dandy, Hopea odorata,

Magnolia conifera, and Calamus tetradactylus Hance

At the site of Thach Thanh district, Thanh Hoa province, the project has set up 2,643 ha

of forest (including 1,277 hectares of indigenous plants, 928 hectares of fast-growing trees, and 438 hectares of regenerated forest) The area of indigenous trees planted under forest

Acacia auriculiformis plantation of KfW4 was selected for planting indigenous trees

under canopy for rehabilitation and conversion, planted in March 2007 (spring season) With

the project site selection, the application of technical measures to grow and care for Acacia

auriculiformis forests is uniform On these areas in March 2011, the project conducted the

planting of indigenous species under the forest canopy as a pilot: Erythrophleum fordii,

Hopea odorata interbedded with A auriculiformis with the density of 450 trees/ha, distance 4

x 6 m Then at the end of 2011 early 2012, the project conducted thinning of Acacia

auriculiformis with the thinning intensity of 40-50%, the current remaining density is about

1,000 trees/ha

1.3.2 Techniques for planting Acacia auriculiformis plantations based on the project regulations

- Mode of planting: pure plantations

- Distance and density of planting

+ Distance: 3mx2m

+ Density: 1,660 trees / ha

1.3.3 Technique for planting indigenous species under the forest canopy

1.3.3.1 Technical procedures for planting Erythrophleum fordii based on the project regulations (2011)

+ Density: 450 trees / hectares

- Seasonal planting: Spring (from February to March)

b Tending and protection

- After planting, Erythrophleum fordii needs continuous tending and protection until the

formation of the forest, especially in the first 4 years

- Times of care: 2 times for spring crops and 1 time for autumn crops

- Tending:

+ Replanting of weak or dead trees: applied for year 1

+ Clearing all climbers, shrubs, weeds and non-PCTs in the planting strips, 1m wide + Cultivating soil around the root: 80 cm wide, 3-4 cm deep

+ Rooting the soil that is applied for 1st and 2nd year

1.3.3.2 Technical procedures for planting Hopea odorata based on the project regulations (2011)

+ Density: 450 trees / hectares

- Seasonal planting: Spring (from February to March)

b Tending and protection

- Replanting of weak or dead trees

+ After planting for 20-30 days, the survival rate should be less than 80%, it must be replanted If more than 80% only replace weak or dead trees (replant) at where dead trees are concentrated, the main planting technique is normal planting

+ In 3 years, if the annual survival rate does not reach 80% of the initial stocking density, then continue to replace weak or dead trees (replant)

CHAPTER 2: OBJECTIVES, CONTENTS AND RESEARCH METHODS

2.1 Objectives of the research

- To assess the growth and quality of some indigenous species planted under the forest canopy in the study area

- To identify factors affecting the growth of indigenous species under the canopy of A

auriculiformis

- To propose some silvicultural techniques to promote the growth of indigenous trees under the forest canopy in the next stage

2.2 Subjects and research methods

- Research subjects of the project are two species: Erythrophleum fordii, Hopea odorata planted under the canopy of Acacia auriculiformis' plantation

- The scope of research: plantation forest in Thach Cam and Thanh Truc communes, Thach Thanh district, Thanh Hoa province

2.2.1 Research methodology on a standard plot

Using topographic maps to conduct a scout survey of the entire study area, locate the

study subjects on the map and record information on the forest status where planted with

Erythrophleum fordii, Hopea odorata and planned to choose the location of the standard plots

to investigate carefully

As a plantation, it should establish 10 rectangular standard plots with an area of 500m2 (25x20m) equivalent to 2% of forest area for each species, representing for 10 different locations of planting indigenous trees

2.2.2 Research on the physical characteristics of soil in the research area

In each standard plot, it should excavate 01 representative profile for the planting area with the dimension of 1.2m long; 0.9m wide; digging deep until seeing soil layers The physical parameters are collected and analyzed including mechanical composition, texture, porosity, moisture

Table 2.1: Forest land profile analyzing results

Profile number: ……… Canopy cover: ………

Mechanical composition

Form/

Structure

Rate

of stone

Rate

of root

2.2.3 Research on the forest structure

a Research on growth characteristics of Acacia auriculiformis

The total height (Ht) and The height under canopy (Huc): Measured by using Forester

Vertex III

The diameter of the canopy (Dc): Using tape measure according to the canopy projection on the horizontal plane Two-way East-West and North-South then calculation the average

Diameter at breast height (D1.3): Measured by tape measure

Canopy cover (CC): On standard plots, we divide the standard plot into parallel lines 2

m apart, on the lines we mark the points 2 m apart Then use a sheet of A4 paper, curled with

a diameter of 3cm, using a fixed tape so that the diameter of the two heads is not changed At these points look up vertically, if encountered the canopy for 1 point, the canopy edge for 0.5 points, no canopy for 0 points, the average of canopy cover is the average value of points of view

Assessment of the quality of indigenous plants by forest plantation monitoring method and evaluation: After data collection, based on the specific growth of each plant and species

in the field, based on the growth criteria (D1.3, Hvn, Ddc, Dt) of each tree and the average growth criteria ( 1.3, ̅t, ̅c, ̅uc) of each species were divided into 3 groups: good, medium, bad

Good trees: These are the trees that have a growth rate that exceeds the proportion of straight stem plants, canopy balanced, well-developed foliage, no pests, not twists, not broken tops

Medium trees: The tree canopies are involved in the forest canopy, but other indicators are less than good trees

Poor trees: The trees are poorly planted; the trees are bent, scattered, pests, broken tops, trees canopy under the forest canopy

Table 2.2: Growth characteristics of Acacia auriculiformis

b Research on growth characteristics of indigenous trees planted under the Acacia auriculiformis canopy

In each plot, we measure D1.3, Ht, Dc of the researched species Specific measurement methods are as follows:

+ Measure diameter at breast height (D1.3) with the tape measure

+ Measure the total height (Ht) with a tape measure from the root to the top of the tree + Measure the diameter of the canopy (Dc) with the tape measure

Good trees: The trees are good growth, straight stem, balance, foliage balanced

development, not pestilent, not twisted, not broken tops

Medium trees: Medium-sized trees, straight stems, canopy, no pests, no breaks

Bad trees: The trees are poorly planted, the trees are bent, scattered, pests, broken tops, trees canopy under the forest canopy

Table 2.3: Growing characteristics of indigenous trees

2.2.4 Methods of data processing

Performing analysis and processing of data by mathematical statistics with the support of Excel software

- Calculation species density (N/ha) according to the formula:

Where: N: plants density / ha

n: average number of plants in the standard plot

S: standard plot area (500m2)

- Characteristics of the sample are calculated by the weighted average formula + Average of the sample:

̅ ∑

̅ ∑

Meaning: ̅ is the avarage value of the sample

: Xi: the value of observed trees

: fi: number of trees at the group I

: n: number of samples

Defining the specialty of the samples (S; S%;…) for research factors

+ Standard deviation: √ ∑ ̅

+ Sample variance: S2 ∑ ̅

Meaning ̅: Sample mean

Xi: the ith element of the sample

N: Sample size

+ Coefficient of Variation: S% =

̅ 100

- Calculation of canopy cover

- Calculation of average annual growth rate of the values:

Meaning: : average value of plot 1

: average value of plot 2

: Standard deviation in plot 1

: Standard deviation in plot 2

: Total number of trees in plot 1

: Total number of trees in plot 2

- If the value of |U| ≤ 1.96 so it leads to conclusion that the growth of 2 samples about are the same, no clearly different

- If the value of |U| ≥ 1.96 so it leads to the conclusion that the growth of 2 samples about have clearly different

CHAPTER 3: NATURAL CONDITIONS OF RESEARCH AREA

3.1 Geographical location

Thach Thanh is a mountainous district in the west of Thanh Hoa province, with geographic coordinates from 20003'50 "to 20023'05" north latitude, from 105014'30 "to

104049'00" east The district center is Kim Tan Town, 60 km northwest of Thanh Hoa

To the North, it borders on Hoa Binh province, Ninh Binh province

To the South borders with Cam Thuy district, Vinh Loc district

To the East borders with Ha Trung district

To the West borders with Ba Thuoc district, Cam Thuy district

There are 9 communes participating in the KfW4 project with a total natural area of 28,479.85 ha This is also the first district to be selected to carry out field activities of the KfW4 project

3.2 Topographic

The terrain of the district is quite complex, severely divided, the land is mainly formed

in place The topography is tilted from northwest to southeast However, alongside the mountains, there are many flat valleys that are convenient for growing crops The average height of the district is from 200 m to 400 m (highest is 825 m, the lowest is 15 m)

Based on the topography, it is possible to divide Thach Thanh district into two terrain areas: High mountains and low hills

+ Mountainous area: Total area: 27,205.46 ha, accounting for 48.65% of the total area

of the district including 8 communes: Thach Lam, Thach Quang, Thach Tuong, Thanh Yen, Thanh Minh, Thach Cam, Thanh My, Thanh Vinh The terrain is complicated and the slope is usually from level III upwards, which is suitable for forestry, perennial and industrial crops

+ Low hills: With an area of 28,713.98 hectares, accounting for 51.35% of the total natural area, has a lower slope and many valleys are favorable for the development of wet rice and industrial crops

According to the data and maps of the province, the area of Thach Thanh district is 49,508.78 ha, including the land used for agriculture/ forestry and the land which has the ability to be combined for agroforestry These areas are divided into slope level as follows:

+ Land with slope level I (<30) 14 066.17 ha

+ Land with level II slope (30 - <80) 5 586.25 ha

+ Land with level III slope (80 - <150) 7 531.66 ha

+ Land with slope of level IV (150 - <250) 10 371.64 ha

+ Land with a slope of level V, VI (> 250) 11 925.46 ha

3.3 Hydrological conditions

Thach Thanh is located in the sub-region of midland in the North of Thanh Hoa province with the following main characteristics (according to data of Thanh Hoa Hydrometeorological Center):

- Temperature: The total annual temperature is from 8.1000C - 8.5000C The amplitude

is from 10 - 120C The daily range is from 7 - 90C Winter temperatures are relatively low, the average January temperature is 15.50C - 16.50C, some places below 150C Summer temperatures are not high The average temperature in July (hottest month) is 270C - 280C

- Rain: The annual rainfall is from 1,600mm to 1,900mm, and the rainfall of crop is accounting for about 86% - 89% The rainfall is the highest in August and September (about 300mm) The lowest rainfall (10mm - 12mm) is in January and February

- Wind speed: average 10 m/s -15 m/s Wind direction is mainly southeast and northeast monsoon In addition, there is a dry southwest wind in weak level

Natural disasters mainly include heavy rain, flash floods, cyclones, heavy cold, and frost

Refer to the water source, there are big dam reservoirs such as Bong Cong (Thanh Minh commune), Dong Ngu (Thanh An commune), Tay Trac (Thanh Long commune), Dong Sung (Thanh Kim commune), …

3.4 Soil

According to the additional survey results issued with the Decision No 756/QD-UBND dated March 7, 2013 approving the results of the project implementation, adjustment and supplement of land map for environmental resources management in Thanh Hoa province with the scale of 1/50,000, there are the following groups and sub-units in the district:

- Gray soil (Acrisol), symbol AC:

+ Typical gray soil of Feralit (AC fa - h) covers an area of 9,754.03 ha, accounting for 17.44% of the natural area, usually at the slope of 80 and over; the layer thickness is over 100

cm The land is suitable for planting the short-term industrial crops at the slope of 80 – 150 and suitable for the long-term industrial crops, fruit trees, agro-forestry and forestry at the slope of over 150

+ Agro-Feralit gray soil (AC fa - L1) covers an area of 23,924.76 ha, accounting for 42.78% of the natural area, distributed on the slope of over 80 The land is suitable for the short-term industrial crops at the slope of <150 and is suitable for the long-term industrial crops, fruit trees, agroforestry and forestry at the slope of > 150

+ Gray soil with deep feralite (AC fa - L2) covers the area of 1,673.37 ha, accounting for 3.00% of natural area The land is suitable for planting the short-term industrial crops at the slope of <150 and suitable for long-term industrial crops, fruit trees, agro-forestry and industrial crops at the slope of > 150

- Fluvisols, symbol FL:

+ Alluvial acacia (FLd- fe1) covers an area of 2,572.98 hectares, accounting for 4.60% of the natural area and is distributed in the high fields This type of land can be used to plant the short-term industrial crops

+ Alluvial soil (FLd - g2) covers an area of 590.04 ha, accounting for 1.06% of the natural area, which is suitable for the development of two rice crops

+ Alluvial soil saturation (FLe - fe1) covers the area of 7,328.22 ha, accounting for 13.10% of the natural area The area is used for rice cultivation and can be used for intensive cultivation with 3 crops

+ Basic soil saturation (FLe - h) covers the area of 2,698.67 ha, accounting for 4.83%

of the natural area The area is capable of intensive farming with 3 crops

+ Alluvial soils (FLd - g2) covers the area of 595.21 ha, accounting for 1.06% of the natural area It is suitable for 2 rice crops

+ Alluvial soil change (FLe - d) covers the area of 371.50 ha, accounting for 0.66% of the natural area It is suitable for 2 rice crops

3.5 Water Resources

- Surface water sources: Thach Thanh has a relatively abundant surface water source, including rainwater at the site and from the place of discharge In the area of Buoi River and other rivers/streams, there are some big lakes and dams supplying water for agricultural production However, surface water is uneven between seasons and months of the year If it is regulated, it will meet the demand for production and life

- Underground water sources: Groundwater here is unevenly distributed, the groundwater is distributed in the different depth levels depending on the terrain Underground water is low, only 0.02 l/s - 2.01 l/s, in the dry season, the groundwater level is low so the soil

is often dry

3.6 Forest resources

Forest area and forestry land in Thach Thanh district is 28,250.89 ha, of which 4,669.60

ha are special-use forests, 6,526.14 ha are protective forests and 17,055.15 ha are production forests

In the district, the area of remaining natural forests is 12,907.49 ha (accounting for 45.6%) The Thach Thanh Natural Forest is rich in plant and animal species, especially Cuc Phuong National Park, which is located in the district

The area of plantations is 11,244.74 ha (39.8%), which is a significant source of income for the district and people in the locality, of which the major part includes plantations of previous programs and projects such as KfW4 and WB3; the Pine area managed by Thach Thanh Protection Forest Management Board will be high-value plantations in the coming period of the district

CHAPTER 4: RESULTS AND DISCUSSION 4.1 Growth characteristics and quality of indigenous trees under the forest canopy in the studied area

4.1.1 Growth characteristics and quality of Erythrophleum fordii

4.1.1.1 Growth characteristics of Erythrophleum fordii

Based on the revised and compiled field data, the results are presented in the table below:

Table 4.1: Growth Characteristics of Erythrophleum fordii (7 years)

S%

̅

(m)

Ht (m)

S%

̅

(m)

Dc (m)

Table 4.2: Comparison of the difference in diameter at breast height (D1.3)

of Erythrophleum fordii between standard plots (U standard)

The average diameter of Erythrophleum fordii in SP 5 at the breast height was 14.68 cm with an average growth of 2.09 cm per year Erythrophleum fordii at SP 1 reached an average diameter at breast height at the lowest point of 5.15 cm per year and increased only 0.73 cm

per year Erythrophleum fordii in the other standard plots have a relatively variable growth rate ranging from 7.74 to 10.21 cm/year

The diameter variation coefficient at breast height of indigenous tree species under the forest canopy of Acacia auriculiformis was the largest at SP5 with 46.1%, indicating that the degree of differentiation in diameter at breast height in SP 5 was quite strong, the second-largest is SP 2 with 40.9% SP 1, SP 3, SP 4 were more uniformly corresponding to 22.7%, 25.1%, 27.1%

Therefore, it can be concluded that the diameter growth at breast height of

Erythrophleum fordii at SP 5 is the best SP 3, 2 and 4 are the slowest SPs The results are shown in the following chart:

Figure 4.1: Comparison of diameter at breast height (D1.3)

of Erythrophleum fordii under the canopy of Acacia auriculiformis

Table 4.3: Comparison of the difference in the total height (Ht)

of Erythrophleum fordii between standard plots (U standard)

The growth of total height of Erythrophleum fordii at 5 SPs was significantly different (U standard calculated from indigenous trees were greater than 1.96, except for U23, U15, and U34) In particular, Erythrophleum fordii in SP 2 is quite high after 7 years reaching 8.85 m with an annual average increase of 1.26 m/year, the next is SP 3 with an average height of 8.33 m increased on average 1.19 m/year and SP 4 reached 7.92 m increase on average 1.13 m/year, the lowest is SP 5 with average height only 5.92 m / year, an average increase of 0.84 m/year

The coefficient of variation (S%) for a total height of standard plots is quite large, the highest is the coefficient of variation of total height of SP 1 up to 32.6%, it leads to the conclusion that the growth of Erythrophleum fordii at SP 1 planted in 2011 has a strong division The coefficient of variation in total height of SP 4, 2, 3 was 16.1%, 18.6%, 20% The

SP 5 fluctuation coefficient of total height was 26.1%

Thus, it can be concluded that the largest Hvn growth in SP 2 is SP 3, SP 4, SP 1 SP 5

is the slowest growth of total height This result is indicated by the following graph:

Figure 4.2: Comparison of the total height (Ht) of Erythrophleum fordii under the

canopy of Acacia auriculiformis

Table 4.4: Comparison of the difference in diameter of the canopy (Dc) of

Erythrophleum fordii between standard plots (U standard)

Evaluation of the growth diameter of the canopy of Erythrophleum fordii in Acacia auriculiformis canopy at standard plots showed no significant difference (only U13 and U35 with U standard calculated higher than 1.96) The diameter of the canopy of Erythrophleum fordii among standard plots clearly showed that the growth of SP 3 is the largest after 7 years reaching 4.37 m with an average growth of 0.62 m/year, the next is SP 2 at 4.07 m with the average growth of 0.58 m/year The following others are SP 4 at 3.9 m, SP 1 at 3.78 m and finally SP 5 at 3.73 m

The diameter of the canopy of Erythrophleum fordii at SP 2 is the largest with 29% indicating the degree of differentiation is quite good The SP 4 fluctuation coefficient was 27%, SP 1 was 24%, SP 3 was 21%, and SP 5 was 17% In conclusion, the growth of Diameter of the canopy of Erythrophleum fordii at 5 standard plots was not significantly different, SP 3 had the highest canopy diameter and SP 5 had the smallest diameter of the canopy

Figure 4.3: Comparison of the diameter of the canopy (Dc) of Erythrophleum fordii

under the canopy of Acacia auriculiformis

4.1.1.2 The quality of growth of Erythrophleum fordii

The quality of the forest is reflected in the number of good, medium and bad trees These are indicative of the ability to adapt to the site conditions

Table 4.5: Percentage of good, medium and bad trees of Erythrophleum fordii forest

Table 4.5 shows the differences in the quality of Erythrophleum fordii in different SPs Details showed below:

- The quality of good trees ranged from 26.3% to 52.6%, the highest at SP 5 with 10 trees

- Besides, the rate of bad quality trees ranged from 4.7% to 42.1%, the highest at SP 4 with 8 trees

- The percentage of trees of medium quality ranges from 30% to 57.1%, the highest at

SP 3 with 12 trees

Examination of differences between standard plots on growth quality of Acacia auriculiformis forests by chi-square test shows that: 2 = 6.83 <  , so the hypothetical is accepted, that means that the growth quality of the Erythrophleum fordii forests at standard plots is not different

4.1.2 Growth characteristics and quality of Hopea odorata

4.1.2.1 Growth characteristics of Hopea odorata

Based on the revised and calculated external survey data, the results are presented in the table as follows:

Table 4.6: Growth Characteristics of Hopea odorata (7 years)

̅

(m)

Ht (m) S%

̅

(m)

Dc (m) S%

Table 4.7: Comparison of the difference in diameter at breast height (D1.3) of Hopea

odorata between standard plots (U standard)

SP 10 10.32 0.87 0.07 0.97

The results in Table 4.6 and Table 4.7 show that the growth of diameter at breast height of Hopea odorata cultivated under the Acacia auriculiformis canopy was not significantly different (U calculation of the standard plots are much smaller than 1.96, only U67, U68, U69, and U610 have the differences) The growth of Hopea odorata at SP 10 is the best with an average diameter at breast height at 13.72 cm, rising at 1.96 m/year, while SP 6 has the slowest growth at 5.98 cm, rising 0.85 m/yr The SP 7, 8 and 9 indicators have grown fairly evenly with 12.83 cm, 12.84 cm, 13.65 cm, growth in diameter breast height ranged from 1.834 to 1.95 m/year

The coefficient of variation in diameter at breast height of Hopea odorata under the canopy of Acacia auriculiformis was rather large, the largest variation was in Hopea odorata

at SP 7 was 26.7% It was demonstrated that the degree of division of the diameter at breast height of Hopea odorata at SP 7 was quite strong, while the coefficient of variation of SP 10 was 23.1% The SP 6, 8 and 9 coefficients were quite similar, respectively, 20.6%, 19.2%, 19.5%, indicating that the growth of these 3 standard plots was fairly uniform

Thus, it can be concluded that the diameter growth factor at 1.3 was the best at SP 10 and is the slowest SP 6, the remaining SP indexes were relatively equal This result is

indicated by the following chart:

Figure 4.4: Comparison of diameter at breast height (D1.3) of Hopea odorata under the

canopy of Acacia auriculiformis

Table 4.8: Comparison of the difference in the total height (Ht) of Hopea odorata

between standard plots (U standard)

OTC6 OTC7 OTC8 OTC9 OTC10

SP 10 6.59 5.46 1.72 1.84

The growth of total height of Hopea odorata at 5 standard plots was different (U

standard of most indigenous species were greater than 1.96, except for U67, U89, U810, and U910) The growth of total height in two SP 8 and 9 are 11.58 m and 11.65 m, increasing 1.65

to 1.66 m/year The growth of total height of SP 10 reaches 10.05 m, up 1.43 m/year SP 6 and 7 having the lowest growth of total height is 5.25 and 6.04 respectively

The coefficient of variation at a total height of Hopea odorata in Acacia auriculiformis forest is quite large, the Hopea odorata coefficient is highest at SP 10 reaching up to 29.4%, 27.3% at SP6, 26.5% at SP7 and 22.3% at SP8 The SP 9 has the smallest coefficient of variation, only reaching 21.7%

Thus, it can be concluded that total height growth of Hopea odorata is highest at SP 10,

SP 8 and 9 have relatively high growth rates, while SP 6 and 7 grow slower than the other standard plots This result is indicated by the following graph:

Figure 4.5: Comparison of the total height (Ht) of Hopea odorata under the canopy of

Acacia auriculiformis

Table 4.9: Comparison of the difference in diameter of the canopy (Dc) of

Erythrophleum fordii between standard plots (U standard)

SP 10 6.14 3.67 0.64 0.51

Evaluation the growth of canopy diameter of Hopea odorata planted under the Acacia auriculiformis canopy at different standard plots showed significant differences (only U89, U810, and U910 had a calculated U value less than 1.96) The canopy diameter of Hopea odorata at SP 10 reaches 4.28 m, the average annual growth of 0.61 m/year The canopy diameter of Hopea odorato at SP 8 and 9 were also well-developed, reaching 4.13m and 4.16m respectively The average canopy diameter of these two standard plots was also very similar at 0.59 m/year The growth of average canopy diameter of SP6 and SP7 was low, reaching 2.81m and 3.3m respectively

The fluctuation coefficient of SP 7 was the highest, reaching 24.4% - it indicated the normal differential; the fluctuation coefficient of SP 10 and SP 6 was 21.6% and 19.5% respectively SP 8 and SP 9 had the lowest coefficient of variation, reaching 12.3% and 12.1% respectively, indicating that the distribution was not high

In conclusions, the growth of canopy diameter of Hopea odorata is fairly uniform, the canopy diameter growth of Hopea odorata is best at SP 8, 9 and 10 The canopy diameter growth of Hopea odorata at SP 6 and 7 is slow The results are shown in the following graph:

Figure 4.6: Comparison of the diameter of the canopy (Dc) of Erythrophleum fordii

under the canopy of Acacia auriculiformis

4.1.2.2 The growth quality of Hopea odorata

The quality of the forest is reflected in the number of good, medium and bad trees These are indicative of the ability to adapt to the site conditions

Table 4.10: Percentage of good, medium and bad trees of Hopea odorata plantations are

summarized in the table:

- In addition, the percentage of bad quality trees in SP 7 is the highest with 3 trees accounting for 14.2% of total SP 7, followed by SP 9 and 10 with 2 bad trees accounting for 10.5% and 9.5% respectively The number of bad trees at SP 6 and SP 8 is the lowest, only a tree accounting for 5.5 - 6%

Examination of differences between standard plots on growth quality of Acacia auriculiformis plantations by standard deviation shows that 2 = 6.79 <  so the hypothetical is accepted, it means that the growth quality of hopea odorata plantation is not different

4.2 Evaluate the factors affecting the growth of indigenous plants

4.2.1 Factors affecting the growth of Erythrophleum fordii

4.2.1.1 The structure and growth of the all plant of Acacia auriculiformis

Table 4.11: Growth characteristics of Acacia auriculiformis forest (Erythrophleum

fordii under the canopy) (11 years)

SP n

N (tree/ha

S%

̅

(m)

Ht (m)

S%

̅

(m)

Dc (m)

Table 4.12: Distribution of growth quality of Acacia auriculiformis plantation

(Erythrophleum fordii under canopy)

- The percentage of trees with average quality varies from 27.6% to 41.6%, with the highest rate in SP 2

Examination of differences between standard plots on growth quality of Acacia auriculiformis plantations by standard deviation shows that 2 = 5.77 <  so the hypothetical is accepted, it means that the growth quality of A auriculiformis at standard plots is not significantly different

4.2.1.2 Characteristics of soil under the forest canopy

The soil is an important factor affecting plants In order to study the effects of soil and topography on the growth of tree species under forest canopy at high-altitude standard plot investigations, the researcher has digged a major cross-section of the standard plot to describe the soil properties

Picture 4.1: Soil profile in Erythrophleum fordii area Table 4.13: Erythrophleum fordii forest land profile analyzing results

Mechanical composition

Form/

Structure

Rate

of stone (%)

Rate

of root (%)

gray Mushy

Quite moist quite rich soil Pellets 5 40

AB 20-27 gray

yellow Medium

Quite moist quite rich soil Pellets 5-20 20

B 27-42 gray

yellow Medium

Quite moist quite rich soil Seed 20-50 0

C 42-50

yellow-brown Tight

Quite moist quite rich soil Seed >50 0

- Location: slopes, slope 10o Slope Direction East-Northeast

- Layer A: 0 - 20 cm, many roots, dark gray soil, moisture, texture, foam, low

percentage of stone, light texture, relatively clear

- Layer AB: 20 - 27 cm, medium roots, yellowish soil, moisture content, texture,

tightness, low stone ratio, light texture, clear layer

- Layer B: 27 - 42 cm, no roots, yellowish soil, damp soil, grain structure, firmness, moderate stone ratio, light muscle composition, clear layer

- Layer C: 42 - 50 cm, no roots, yellowish brown soil, moisture content, grain structure, tightness, a high proportion of stone, mechanics of light meat, clear layer

Discussion

The soil in the studied area is dark gray to brownish yellow, growing on limestone and claystone, with an average thickness of <50cm, acid soil, moisture, tightness, medium soil, humus, phosphorus, nitrogen, potassium mainly from medium to poor

4.2.2 Factors that affect the growth of Hopea odorata

4.2.2.1 The structure and tall plant growth of Acacia auriculiformis

Table 4.14: Growth characteristics of Acacia auriculiformis (Hopea odorata under

S%

̅

(m)

Ht (m)

S%

̅

(m)

Dc (m)