MINISTRY OF AGRICULTURE AND RURAL DEVELOPMENT
VIETNAM FORESTRY UNIVERSITY

STUDENT THESIS

PLANT COMMUNITIES OF MANGROVE FORESTS IN DONG LONG
COMMUNE, TIEN HAI DISTRICT, THAI BINH PROVINCE

Major: Natural Resources Management
Code: D850101
Faculty: Forest Resources and Environmental Management

Student: Nguyen Thi Hien

Student ID: 1153090344

Class: K56 Natural Resources Management

Course: 2011- 2015

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

Supervisor: Dr. Vu Quang Nam

Hanoi, October 2015


ACKNOWLEDGEMENT
Foremost, I would like to express my sincere gratitude to my advisor Dr. Vu Quang
Nam for the continuous support of my student thesis study and research, for his motivation,

enthusiasm, and immense knowledge. His guidance helped me in all the time of research and
writing of this thesis.
Beside my advisor, I would like to thank professor from Colorado State University, Dr.
Lee Macdonald, for his guidance, patience, and providing my class with an excellent
atmosphere for our research. My sincere thanks also goes to Mr. Nguyen Xuan Nho- leader
of mangrove forest protection, who provided me many useful knowledge about mangrove
forest and all of officers in Dong Long commune, for their giving information about the local
area and culture that helped me a lot in this study.
Lastly, I would like to thank to my family: my mother who always support to me and
my friends who helped me in my research.
Hanoi, October 2015

Nguyen Thi Hien


CONTENTS
ACKNOWLEDGEMENT
ABSTRACT
1. INTRODUCTION .................................................................................................................. 1
2. GOALS AND SPECIFIC OBJECTIVES .............................................................................. 5
2.1. Goal .................................................................................................................................. 5
2.2. Specific objectives ........................................................................................................... 5
3. STUDY SITE AND METHODS ........................................................................................... 6
3.1.

Study site...................................................................................................................... 6

3.2. Methods ........................................................................................................................... 7
3.2.1. Field work: ................................................................................................................ 7
3.2.2. Data analysis methods: ............................................................................................. 9

4. RESULTS AND DISCUSSIONS ........................................................................................ 11
4.1. Species composition of vascular plants and their distribution ....................................... 11
4.1.1. Species composition of vascular plants in Dong Long commune ........................... 11
4.1.2. Diversity of flora in Dong Long .............................................................................. 12
4.1.3. The valueable uses ofvegetation in Dong Long ...................................................... 13
4.1.4. Distribution of vegetation in Dong Long ................................................................ 14
4.2. Assemblages and mangrove forest communities and their distribution in Dong Long . 15
4.2.1. Species density......................................................................................................... 18
4.2.2. Community structure ............................................................................................... 19
4.2.3. Distribution of mangrove forest communities in Dong Long .................................. 23
4.3. Predict plant succession in Dong Long.......................................................................... 23
5.

CONCLUSION AND RECOMMENDATION ................................................................ 26
5.1.

Conclusion ................................................................................................................. 26

5.2.

Recommendation ....................................................................................................... 26


REFERENCES
APPENDIX
Appendix A: Table
Appendix 2: Figure


LIST OF TABLES

Table 4.1. True mangrove species in 3 lines ............................................................................ 12
Table 4.2. The life form of mangrove vegetation in Dong Long ............................................. 13
Table 4.3. The valuable uses of vegetation in Dong Long ....................................................... 14
Table 4.4. Distribution of vegetation in Dong Long commune................................................ 15
Table 4.5. Composition some mangrove lines follow to plots ................................................. 16
Table 4.6. Mangrove plant communities in 3 lines .................................................................. 17
Table 4.7: Tree density in communities, assemblages in Dong Long commune ..................... 18
Table 4.8. Species compositions in three communities............................................................24


LIST OF FIGURES
Figure 3.1. Study site .................................................................................................................. 6
Figure 3.2: Standard plots are set up on survey line ................................................................... 8
Figure 4.1. Vertical profile in line 1 ......................................................................................... 20
Figure 4.2. Cross profile in line 1 ............................................................................................. 20
Figure 4.3. Vertical profile in line 2 ......................................................................................... 21
Figure 4.4. Cross profile in line 2 ............................................................................................. 21
Figure 4.5. Vertical profile in line 3 ......................................................................................... 22
Figure 4.6. Cross profile in line 3 ............................................................................................. 22
Figure 4.7. Primary succession of mangrove vegetation in Dong Long Commune ................. 25


ABSTRACT
Mangrove at Dong Long Commune constitutes a mangrove flora that contributes to
the biodiversity in the coastal region referred to as the Tien Hai coastal. This research
concentrates on three objectives: descriptive the vascular species composition and
distribution of the mangrove flora in Dong Long Commune; determine assemblages, plant
communities and their distribution; predict plant succession.
To conduct these objectives above, the research established 3 survey lines is
perpendicular with the sea dike and set up 9 standard plots representing the study area, each

plot has area with 500 m2 (20x 25m) along the transect line.
From the results collected, I constructed the list of vascular plants including 51
species belonging to 49 genera of families in 2 phyla, including 7 true mangrove species, 14
mangrove assosicated species and 28 immigrant local species which were distributed to
coastal saline areas. They distribute in 5 main regions: regular intertidal zone;irregular
intertidal zone;sands sludge formation and improvements;improvement sand area less tidal
and coastal shrimp farms, road and sea dike.There are three communities in study site:
Sonneratia caseolaris - Kandelia candel - Acanthus ebrateatus(Sc- Kc- Ae), Acanthus
ebrateatus - Aegiceras corniculatum - Sonneratia caseolaris (Ae- Ac- Sc)and Aegiceras
corniculatum - Kandelia candel - Acanthus ebrateatus – Sonneratia caseolaris(Ac- Kc- AeSc). Over time, mangrove succession have trend to the sea with the pioeer is Sonneratia
caseolarisand Aegiceras corniculatum.


1. INTRODUCTION
Mangrove forests play an important ecological role in the coastal environment. They
not only prevent erosion of dykes from waves and storms by stabilizing sediments with their
tangled root systems, but also maintain water quality and reduce pollution. Moreover,
mangrove forests are rich in biodiversity with many animals living there such as marine
creatures, birds, mammals, and reptiles.
Rapid population growth, the development of aquaculture activities, reclaiming land
for rice fields, and the rapid development of infrastructure in urban areas have caused
degradation mangrove plant ecosystems in Vietnam. In the period from 1943 to 1999, the
mangrove forest area in Vietnam has decreased from 409.000 ha to 155.000 ha (62%), due to
the destruction of wars and development of extensive shrimp farms.
Dong Long Commune belongs to Tien Hai District. It has a total area of 7.83 km2
and has a total population of 5010 people (Ministry of Information & Communications,
2012). This is one of 4 communes in Tien Hai District with relatively large mangrove
forests. Many years ago, due to the development of extensive shrimp farms, mangrove forest
areas shrunk and the vegetation were degraded. That is why many coastal dyke systems in
Dong Long Commune were eroded and broken when a storm came in 1996 (information

from data of Tien Hai Nature Reserve). Some projects have been established to improve
mangrove forest such as Program 327, and especially project supported by the Red Cross in
Denmark for planting mangrove forest. This project not only helps protect coastal dykes, but
also improves the local people’s life. Local people have earned income through planting
mangrove plants and harvesting sea food from mangrove forest. Red Cross in Denmark
supported 51.7 ha of Kandella and 94.82 ha of Kandella, Rhizophora, and Sonneratia. This
leads to the improvement of the mangrove ecosystem and more diversity of sea food species
in Dong Long. However, as the complicated of climate change occur such as temperature

1


increases and sea level rises…, the mangrove forest area in Thai Binh, especially in Dong
Long, needs to be protected and developed more and more.
To support the restoration and development of mangrove forest, we need to
determine the composition of plant species, their association, communities, and their
distribution in mangrove forest. From that, we gain an overview about the rules of changing
in the structure of mangrove forests and also mangrove forest succession. This is the basic
technical solution to develop mangrove communities.
Mangrove forest in the world:
Mangrove forests distribute mainly on the equator and 2 sides tropical hermisphere.
However, some species expand up to 32o22’North (Bermuda) such as Rhizophora stylosa,
Kandelia candel, and Bruguiera gymnorrhiza (Le V.H, 2005).
There is much research on mangrove forest in the world. P.V.Richard has many
studies inareas of South America, Central Africa, and Southeast Asia. Especially, he has
researched about “Tropical rainforest”.In this study; the authors have studied landforms,
structures, components, and natural conditions (soil, climate ...) of the tropical rain forest,
including mangroves.
After many experiments and observation about dispersal and regeneration of some
mangrove species in Panama, Rabinowitz (1975) said that the number of young dominant

mangrove species in low tide is bigger than in highland and need the time for scattering and
fixing trees. He also thinks that the mortality of propagules is inversely proportional to their
masses. When the seedlings have fixed and started growth, they usually grow poorly below
the shade of tall trees (Nguyen T.T.H, 2006).
Kasawani et al (2007) studied the forest structure, diversity index, and biomass of
forest mangrove in Tok Bali, Kenlanta, Malaysia. The authors tried to find out the structure
of mangrove distribution to establish a recovery and management program. The result shows
that Sonneratia alba is a dominant species with more than 73 trees in each transect line.
2


Suwa et al (2009) researched the structure of a subtropical mangrove forest along
Okukubiriver in Okinawa Island, Japan based on biomass and tree height. The research
shows that the reduction of biomass and tree height does not necessarily reflect the leaf
photosynthesis and development of mangrove trees.
Mangrove forests in Vietnam:
Vietnam is locacated in a tropical climate with advantages for mangrove forest
development. Before 1943, there were about 400,000 ha of mangrove forest areas in
Vietnam, but after 1975, there were only 185,877 ha left due to many different reasons such
as war, mining, and unsustainable management of mangrove forests.
Phan N.H (1999) published a plant species composition of Vietnam’s mangrove
ecosystems which include 77 mangrove species of 2 environmental groups, and various life
forms. Group I has 35 mangrove species belonging to 20 genera of 16 families, this group is
often called the "true" mangrove group. Group II consists of 42 species belong to 36 genera
of 16 families, this group includes "joiner" species in the mangroves and they often live in
secondary forest and highland. Phan Nguyen Hong also was the first scientist in Vietnam to
mention the geographical distribution and mangrove community’ssuccession in many
researches. In our country’s mangrove ecosystem, there are 45 mangrove forest
communities, and 6 mangrove forest populations distributed in different regions.
In recent years, Vietnam has produced much research about mangrove forest. Vu D.T

et al (2003) studied mangrove forest in 3 different ages at Giao Lac, Giao Thuy, and Nam
Dinh. He thinks that Kandelia forest in ages from 4 to 6, and planted in distance of 0.7 x
0.7m have better tree diameter and height.
Dao.V.T et al (2005) investigated some characteristics of mangrove plant
communities in Dien Chau, Nghe An. He listed a total of 40 species belonging to 37 genera
of 24 vascular families’ distributed in the mangroves at study area. The research has also

3


mentioned some species that participate in mangrove forest composition in Dien Chau, and
divided them into 8 typical species communities with high value in the study area.
Hoang V.T (2005) studied mangroves structure and the relationship between
mangrove vegetative distribution and frequent tidal mangrove forest in Ca Mau to conclude
that: the study area has 12 states of mangrove forest with 72 species belong to 40 families.
True mangroves group includes 23 species belonging to 12 families; the tree participation
group includes 49 species belonging to 28 families. Sonneratia alba and Avicennia
officinalis are dominant tree species, and Rhizophora forest is the largest area.
Nowadays, due to the global climate changes, forest ecosystems research is very
essential. Especially in riparian areas, and coastal areas, the study of mangrove ecosystems
also plays an important role. Studies on mangroves will provide necessary materials for
construction, restoration, and protection. Mangrove plant communities are important
segments in the study of mangrove ecosystems. On the other hand, they always change
succession phases; therefore, studies about the characteristics of mangrove forests are
essential and have highly practical significance. Hence, I decided to choose the title: “Plant
communities of mangrove forests in Dong Long Commune, Tien Hai District, Thai
Binh Province”.

4



2. GOALS AND SPECIFIC OBJECTIVES
2.1. Goal
To provide the scientific basic for usage, conservation and development of mangrove
forest resources in Dong Long, Tien Hai, Thai Binh Province.
2.2. Specific objectives
- Determine the species composition of vascular plants and their distribution among
communities of terrestrial and intertidal zones in the study area;
- Identify assemblages, plant communities, and their distribution in mangrove forests
in Dong Long;
- Give a prediction about plant succession in the study area to determine whether
mangrove vegetation will reach to the sea or not.

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3. STUDY SITE AND METHODS
3.1. Study site
Dong Long Commune is located in Tien Hai District, Thai Binh Province. It is far
from Tien Hai Town about 10km. Geographical coordinate: 20o26’55’’ North latitude;
106o36’5” East longtitude.
The East borders with sea
The West borders with Dong Xuyen and Dong Tra Commune
The South borders with Dong Hoang Commune
The North borders with Dong Hai Commune

Figure 3.1. Study site: Dong Long Commune, Tien Hai District, Thai Binh Province
Dong Long Commune covers a total area of 7.83 km2. The population in 1999 was
5010 people, with a population density of 640 people per km2 (Wikipedia). Dong Long is
located in a tropical mooson climate. However, Dong Long is also affected by coastal

6


climate because it is near the sea. The annual average temperature of the region is 23 - 24oC,
the highest temperature is 39oC. The average annual rainfall is from 1500 to 2000mm and
mostly in summer. The rainfall accounts for 80% of annual rainfall. In summer, the highest
rainfall can reach from 200 to 350 mm per day. The dry season lasts from October to March
with a total rainfall about 20% of the annual rainfall. The air humidity fluctuates from 82 to
90%. In summer, the main wind direction is southeast wind, and the average wind speed is
from 2 to 5m per second. This time often has storms from June to October, mostly in August.
Each year has from 4 to 6 storms, with an average wind force from 8 to 11, causing major
damage to productive activities and people's life.
3.2. Methods
3.2.1. Field work:
I had one month in Dong Long commune to survey the field. After surveying
generally, I chose 3 typical lines in study site to set up survey lines. Each line corresponds
with one plant community or assemblage.
 Set up survey lines
In each community I chose one typical area to establish survey lines following to
Aksornkoae and Kongsangchai (1987) and each survey line is perpendicular with the sea
dike (from the sea to dike).
 Set up standard plots on survey line
On each survey line, I selected 3 typical locations in the study area and distance from
sea to dike is about 50m, 150m and 250m to set up 3 plots (Plot 03; Plot 02; Plot 01) and
each plot has an area with 500 m2 (following to Nguyen V.C, 2014). The plots are
established by tape and right angle. Boundaries of plot are defined by 4 wood stakes at 4
corner of each plot and after that I stretched a cord around 4 stakes to recognize each plot.

7



Figure 3.2: Standard plots are set up on survey line

In each plant community I set up 3 plots and determined the species component, the
number of each species and total number of trees. The information was recorded:
 Number of standard plots, the area of survey plots, date of investigation, investigator,
distance to edge (m)…
 Measure and classify wood trees, shrubs and grasses: note all of trees in plots survey and
take specimens of unknown trees to investigate. Measuring trees density (trees/plot), tree
height, canopy height, canopy diameter of all wood trees having D1.3≥ 3cm and location of
trees in plots.
 Profile diagram
Each line chooses one typical forest strip to draw. Area’s strip is 10m x 25m (25m is length
of plot paralleling seaside and 10m is depth). Profile diagram is drawn based on method of
Richards P.W and Davis T.A.W (1933- 1934).
 Profile diagram is drawn on paper; it is conducted with measuring trees and drawn one by
one.
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 Standing profile: draw the near trees first and the far trees after, the trees in front are
drawn solid lines and the trees in behind are drawn disjointed lines.
 Cross profile: draw tree canopy on all plot area, the highest trees are drawnsolid lines and
shorter trees are drawn disjointed lines.
To draw profile diagram, we need to measure tree index as trees height, trees canopy
in 2 directions (South North- East West), coordinate trees (distance between stumps with 2
sides of plot) and shape of trees. Name of trees drawn on profile diagram should be noted on
tree canopy (note if name of trees abbreviate).
 Take photograph and collect necessary specimens in investigation process in order to
analysize and assess scientific name.

3.2.2. Data analysis methods:
+ Statistical table about components and species compositions (following to Nguyen N.T,
2007).
+ Assessing scientific name: by the method of morphological comparisons between
specimens collected with documents related to plant such: Vegetation of Vietnam (Pham
H.H, 1999-2000), Forest tree name of Vietnam (Vu V.D, 1996), Plants in mongroves of
Vietnam (Nguyen H.T, 1996)...
 Sort tree species in family order according to the classification system of Takhtajan
(2009).
 Determine assemblages and communities in the study area.
 Analyze and evaluate the data obtained, compare with the published documents.
+ Species composition of mangrove: divide into 3 main groups: True mangrove species
(MS), Mangrove associated species (MAS) and Immigrating local species (ILS) (base on
dividing mangrove group of Nguyen N.T et al (2001).
+ Determine the distribution of mangrove vegetation following to 5 main groups: regular
intertidal zone, irregular intertidal zone, sands sludge formation and improvements,
9


improvement sand area less tidal and coastal shrimp farms, road and sea dike based on
separation of Phan K.L and Nguyen T.H (1998).
+ Analyze data by excel 7.0 software
3.2.2.1 The tree compositions
Determine coefficient composition of each species calculated by:
The coefficient composition

With:

K is coefficient composition
n is the number of individual species in the study area

N is total individual species in communities

From that give the composition formula of each.
3.2.2.2. Density
⁄
With:

=

N: is number of individual species or total individual species in standard plot
S: is area of plot (m2).

3.2.2.3. Predict Plant succession in the study area
Predicting plant succession in the study area was assessed based on Vu T.T (2000).
Based on these results from plant composition, distribution, communities… will predict the
plant succession in study area.

10


4. RESULTS AND DISCUSSIONS
4.1. Species composition of vascular plants and their distribution
Although the intertidal zone is swampy, wide and has a lot of silt, along coastal do
not have stands of native mangrove forest. The factors preventing mangrove forest formation
that along coastal are moonsons and storms (P.N.Hong and H.T. San 1993).
Through investigating and interviewing local people I saw that the mangrove forest
in Dong Long is forest planting. For a long time, coastal people here planted stands of
Sonnaeratia, Kandelia candel, Aegiceras corniculatumand Acanthus ebrateatusto protect
dykes, houses and farms. After a few years these mangrove plants grow and regenerate
naturally and quickly in the intertidal zone.

4.1.1. Species composition of vascular plants in Dong Long commune
The research results have identified 51 species of plants; belonging to 49 genera, 13
families of 2 phyla: Polypodiophyta, Magnoliophyta. The research result is presented in
appendix 01.
Species composition of mangrove appendix shows that MS group includes 7 species,
which belong to 6 plant families; accounting for 13.7% of total species. MAS group includes
15 species, which belong to 14 plant families; accounting for 29.4% of total species.
Remaining is 29 immigrant local species which belong to 10 families, accounting for 56.9%
of total species.
Compared with plant list of Phan N.H (1999) (106 species of mangroves- 36 true
mangrove species and 70 mangrove associated species), mangrove species composition in
Dong Long is less diverse with 51/106 (representing 48.1%) of all mangrove species in
Vietnam (not accounting for immigrant local species).
Based on evaluating mangrove forest criteria of Pham Nhat et al. (2003) and FAO
(2007): the diversity of mangrove forest is low with 1- 3 species in forest, greater than 10
species is high diversity. Therefore, we can conclude that mangrove plants in Dong Long are
11


less diverse. In there, 7 main mangrove species arranged in descending order of quantity are
Sonneratia caseolaris (Bần chua), Kandelia candel (Trang), Aegiceras corniculatum (Sú),
Acanthus ebrateatus (Ơ rơ), Acrostichum aureum (Ráng đại), Excoecaria agallocha (Giá),
Rhizophora stylosa (Đước vòi). Sonneratia caseolaris, Kandelia candel, Aegiceras
corniculatum, and Acanthus ebrateatusare 4 typical species with high quantity and belong to
3 research lines (table 4.1).
Table 4.1. True mangrove species in 3 lines
Survey lines

Vietnamses
Scientific name

name

Line 1

Line 2

Line 3

Sonneratia caseolaris

Bần chua

+++

++

+

Kandelia candel

Trang

+

+++

++

Aegiceras corniculatum


Sú

0

++

+++

Acanthus ebrateatus

Ơ rơ

+

+

++

Rhizophora stylosa

Đước vịi

0

+

0

Note: 0: absent; +rare; ++ average; +++ abundant
From table 4.1 we can see the species that appear at all 3 lines are Sonneratia

caseolaris, Kandelia candel and Acanthus ebrateatus.Appearing at 2 lines is Aegiceras
corniculatum. Rhizophora stylosa just appears at only 1 line and has only 1 tree. We can
conclude that Sonneratia caseolaris, Kandelia candel, Acanthus ebrateatus and Aegiceras
corniculatum are 4 species adapting with natural condition in Dong Long commune.
4.1.2. Diversity of flora in Dong Long
Beside true mangrove species, Dong Long also has associated and immigrant local
species. They created an ecosystem with many different structure and life form. According
to Ministry of Agriculture and Rural Development (2000) " Forest tree name of Vietnam ",

12


Hoang Chung (1980) about plant’s life form, I divided them into 4 life forms: Wood, Shurb,
Herb and Liana. The research results are shown in table 4.2.
Table 4.2. The life form of mangrove vegetation in Dong Long
No. of
No.

Life form

Symbol

Rate (%)
species

1

Wood

W


11

21.6

2

Shrubs

S

16

31.4

3

Lianas

L

2

3.9

4

Herbs

H


22

43.1

51

100

Total

Table above shows that the life form having highest rate is herb, accounting for
43.1%of total species. The main species belong to Asteraceae family and Amaryllidaceae
family and they usually live in dyke edge, coastal shrimp farms and road.Shrubs group
accounting for 31.4%. The main shrub groups are species as Aegiceras corniculatum,
Acanthus ebrateatus, Clerodendrum inerme and some species belong to Solanaceae family.
Wood life forms account for 21.6% after Herb and Shrub group and main species belong to
True mangrove species as Sonneratia caseolaris, Kandelia candel, Excoecaria agallocha
(Giá) and Mangrove associated species like Hibiscus tilliaceus (Tra làm chiếu). Liana just
accounts for 3.9% includes Ipomaea pes carpae and Canavalia lineate.
4.1.3. The valuable uses ofvegetation in Dong Long
The research results have identified that mangrove plant in Dong Long have 50
species and all of them have valuable use such as: medicical, food, timber and firewood,
bonsai, food, attar...

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Table 4.3. The valuable uses of vegetation in Dong Long
Number

Rate
No.

Valuable uses

Sign

of
(%)
species

1

Medical

M

44

86.3

2

Timber, firewood

TF

9

17.6


3

Bonsai

B

11

21.6

4

Food

F

11

21.6

6

11.8

Tamin, Attar (tinh dầu), dye (thuốc
5
nhuộm)

A


6

Toxic

T

3

5.9

7

Differences (fibre, beekeeping)

D

3

5.9

Note: Total does not equal 51 species because one species can have many valuable uses.
M: Medical; TF: Timber, firewood; B: Bonsai; F: Food; A: Attar; T: Toxic; D: Different
Looking at table above, we see that all plants in Dong Long commune have many
valuable uses. The number of plants having medicinal value is largest at 86.3%, the majority
belong to herbs and shrubs life forms and they usually live around dyke and highland.
Bonsai and food values account for 21.6% and timber, firewood accounts for 17.6%. Others
value just account for from 6 to 12%.
4.1.4. Distribution of vegetation in Dong Long
From research results collectedin appendix 01, distribution of vascular plants in Dong

Long commune is divided into 5 main groups: regular intertidal zone, irregular intertidal
zone, sands sludge formation and improvements, improvement sand area less tidal
andcoastal shrimp farms , road and sea dike.

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Table 4.4. Distribution of vegetation in Dong Long commune
Number
Rate
Species distribution

Symbol

of
(%)
species

Regular intertidal zone

1

5

9.8

Irregular intertidal zone

2


10

19.6

Sands sludge formation and improvements

3

4

7.8

Improvement sand area less tidal

4

12

23.5

Coastal shrimp farms, road and sea dike

5

45

88.2

Note: Total does not equal 51 species because one species can live in many regions.
Base on data in table above, we can see that vegetation in Dong Long distribute

mainly in coastal shrimp farms, road and sea dike with 88.2%. The main species in this
group are immigrant local species. Irregular intertidal zone and Isand area less tidal account
for 19.6% and 23.5%. Two remaning location account low rate are sands sludge formation
and improvementsand regular intertidal zone with 7.8% and 9.8%. The main species in
living here belong to true mangrove group such as Sonneratia caseolaris, Kandelia candel,
Acanthus ebrateatus and Aegiceras corniculatum.
4.2. Assemblages and mangrove forest communities and their distribution in Dong Long
To determine mangrove communities at Dong Long commune, I conducted an
investigation species composition of 3 lines that is perpendicular to seaside. The results were
showed in table 4.5.

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Table 4.5. Composition some mangrove lines follow to plots
Line

Plot
01
02

1
03

Species

Rate

Sonneratia caseolaris


100.0%

Sonneratia caseolaris

76.4%

Kandelia candel

23.6%

Sonneratia caseolaris

83.9%

Kandelia candel

11.8%

Acanthus ebrateatus

4.3%

Average
04

2

05

06


Aegiceras corniculatum

87.8%

Sonneratia caseolaris

12.2%

Acanthus ebrateatus

54.8%

Sonneratia caseolaris

22.6%

Aegiceras corniculatum

22.6%

Acanthus ebrateatus

88.9%

Sonneratia caseolaris

11.1%

3


Aegiceras corniculatum

86.4%

Kandelia candel

10.7%

8.8 Ac+1.2Sc

5.5 Ae +2.3Sc + 2.3 Ac

8.9 Ae +1.1Sc

8.6 Ac + 1.1 Kc+ 0.3Sc

2.9%

Kandelia candel

65.8%

Aegiceras corniculatum

31.9%

Sonneratia caseolaris

09


8.4Sc + 1.2 Kc + 0.4 Ae

7.2Ae+ 5.5Ac+1.5Sc

Sonneratia caseolaris

08

7.6Sc+ 2.4 Kc

8.7Sc+ 1.8Kc + 0.4Ae

Average

07

Composition formula

6.6 Kc + 3.2 Ac + 0.2Sc

2.3%

Aegiceras corniculatum

66.7%

Acanthus ebrateatus

20.2%


Kandelia candel

11.5%

Sonneratia caseolaris

6.7 Ac + 2 Ae+ 1.2 Kc+ 0.16Sc

1.6%

Average

6.2Ac + 2.9Kc + 2Ae+ 0.22Sc

Note: Ac: Aegiceras corniculatum; Ae: Acanthus ebrateatus; Sc: Sonneratia caseolaris;
Kc: Kandelia candel.

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Based on data composition in 3 line surveys, I determined 3 mangrove communities
corresponding with the lines 1, 2, 3 are:
- Line 1: Sonneratia caseolaris - Kandelia candel - Acanthus ebrateatus
- Line 2:Acanthus ebrateatus - Aegiceras corniculatum - Sonneratia caseolaris
- Line 3:Aegiceras corniculatum - Kandelia candel - Acanthus ebrateatus - Sonneratia
caseolaris
Table 4.6. Mangrove plant communities in 3 lines
Lines


Communities

1

Sc- Kc- Ae

2

Ae- Ac- Sc

3

Ac- Kc- Ae- Sc

Communities Sc- Kc- Aelines on first transect line and the results show that there are
3 species Sonneratia caseolaris, Kandelia candel and Acanthus ebrateatus. Sonneratia
caseolarisis dominant species, accounting for 7.6 ÷ 10, Kandelia candel accounting for 1.2 ÷
2.4 and Acanthus ebrateatusaccounting for 0.4. Moreover, plot 1 just only apprear
Sonneratia caseolariswithout having the appearance of the other species. Plot 2 has the the
appearance of Sonneratia caseolaris, Kandelia candel and dominant species is also
Sonneratia caseolaris with 7.6, Acanthus ebrateatus is absent in this plot.
The second line includes 3 species Acanthus ebrateatus, Aegiceras corniculatum,
Sonneratia caseolarisand Acanthus ebrateatus is dominant species accounting for 5.5 ÷ 8.9,
Aegiceras corniculatumaccounts for 2.3 ÷ 8.8 and Sonneratia caseolaris has low rate with
1.1 ÷ 2.3. Plot 4 appears 2 species are Aegiceras corniculatumand Sonneratia
caseolariswithout having Acanthus ebrateatus and in this plot Aegiceras corniculatumis
dominant accounting for 8.8. Plot 6 appears Acanthus ebrateatus and Sonneratia caseolaris

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without

appearing

Aegiceras

corniculatumand

the

dominant

species

isAcanthus

ebrateatusaccounting for 8.9.
Comparing with 2 lines above, the number species appears in line 3 is the most
including 4 speciess area: Aegiceras corniculatum, Acanthus ebrateatus and Sonneratia
caseolaris andKandelia candel. In this line, Aegiceras corniculatumis dominant species
accounting for 3.2÷ 8.6; Kandelia candel accounts for 1.1 ÷ 6.6; Acanthus
ebrateatusaccounts for 2 and Sonneratia caseolaris has low rate is 0.16 ÷ 0.3. There has only
plot 9 including 4 species above, plot 7 and plot 8 just appear 3 species are Aegiceras
corniculatum, Kandelia candel and Sonneratia caseolaris.
4.2.1. Species density
Forest density is important factor impacting to forest formation and living space
potential of site conditions. In the entire process of formation, growth and development of
the forest, the density is constantly changing factors.
Through investigation on structure density of mangroves in research area, the results

are summarized in the table 4.7.
Table 4.7: Tree density in communities, assemblages in Dong Long commune
Communities

Plots

Density
Trees/plots

Trees/ha

1

23

460

2

72

1440

3

93

1860

Average


63

1253

4

262

5240

5

212

4240

6

63

1260

Average

179

3580

7


242

4840

8

354

7080

9

183

3660

Average

259

5193

Sc- Kc- Ae

Ae- Ac- Sc

Ac- Kc- Ae- Sc

18