Plant diversity and structure of mangroves in hai ha district quang ninh province

This research concentrates on three objectives: descriptive the biodiversity species and role of mangroves forest in Hai Ha district; determine species composition, structure and distrib

ACKNOWLEDGEMENT

First and foremost, I would like to express my sincere gratitude to my advisor Assoc Prof 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 Van Hieu- vice-leader of mangrove forest protection, who provided me many useful knowledge about mangrove forest and all of officers in Hai Ha district, 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 father who always support to me and

my friends who helped me in my research

ABSTRACT

Mangrove at Hai Ha district constitutes a mangrove flora that contributes to the biodiversity in the coastal region This research concentrates on three objectives: descriptive the biodiversity species and role of mangroves forest in Hai Ha district; determine species composition, structure and distribution of the mangrove flora in Hai Ha district; proposed some solutions to protect and develop sustainable mangrove forest

To conduct these objectives above, the research established 6 survey lines is perpendicular with the sea dike and set up 18 standard plots for six communes in Hai Ha District, each plot has area with 400 m2 (20x 20m) along the transect line

From the results collected, I constructed the list of vascular plants including 41 species belonging to 26 genera, 10 main mangrove species and 31 species living in mangrove forest 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: Avicennia marina - Rhirophora stylosa - Aegiceras corniculatum (Am - Rs - Ac), Aegiceras corniculatum - Bruguiera gymnorrhiza - Rhirophora stylosa (Ac - Bg - Rs) and Aegiceras corniculatum - Avicennia marina - Rhirophora stylosa (Ac - Am - Rs) Over time, mangrove succession have

trend to the sea and we need some solutions to protect and develop sustainable mangrove forest in Hai Ha district

TABLE OF CONTENTS

CHAPTER I INTRODUCTION 1

CHAPTER II LITERATURE REVIEW 4

2.1 Mangrove forest in the world 4

2.2 Mangrove forests in Vietnam: 6

CHAPTER III STUDY GOAL, OBJECTIVES, SCOPE OF THE STUDY AND METHODOLOGY 9

3.1.1 Goals: Assessment of biodiversity and structure of coastal mangrove forests, which proposed several solutions to contribute to better management of coastal mangroves 9

3.1.2 Specific Objectives: 9

3.2 SCOPE OF THE STUDY 9

3.2.1 Geographical location, topography 9

3.2.2 Climate: 10

3.2.3 Hydrology: 11

3.2.4 Salinity: 12

3.2.5 Soil conditions: 12

3.3 CONTENTS AND METHODOLOGY 14

3.3.1 Research Content 14

3.3.2 Methodology 14

3.3.2.1 Data collection method: 14

CHAPTER IV RESULTS AND DISCUSSION 19

4.1 DIVERSITY OF MANGROVE FORESTS IN COASTAL AREA HAI HA DISTRICT, QUANG NINH PROVINCE 19

4.1.1 List of mangroves in the study area 19

4.1.2 Value of mangrove forest 27

4.2 DISTRIBUTION AND STRUCTURE OF MANGROVE FORST IN COASTAL

AREA HAI HA DISTRICT, QUANG NINH PROVINCE 33

4.2.1 Characteristic and distribution of mangrove forest in Hai Ha district 33

4.2.2 Combination of species 35

4.2.3 Species density 40

4.2.4 Stratified structure 41

4.3 PROPOSING SOME SOLUTIONS TO USE SENSIBLY, PROTECT AND DEVELOP HAI HA MANGROVE FOREST 45

4.3.1 Status of mangrove forest in Hai Ha district 45

4.3.2 Proposing some solutions to use, protect and develop Hai Ha Mangrove forest 45

CHAPTER V GENERAL CONCLUSION AND RECOMMENDATION 50

5.1 Conclusion 50

5.2 Recommendation 50

REFERENCES 50

APPENDIX 52

LIST OF TABLES

Table 3.1: The area of tidal ground has salt-marsh vegetation in Hai Ha district 13

Table 4.1 List of mangroves in 6 coastal communes in Hai Ha district, Quang Ninh province 19

Table 4.2 Numbers of species in phyla and classes found in Hai Ha mangrove forest 23

Table 4.3 Life forms of mangrove plants in Hai Ha district, Quang ninh provice 26

Table 4.4 Values of mangrove species in Hai Ha district 30

Table 4.5 Groups of valuable plants in Hai Ha mangrove forest 32

Table 4.6 Composition of mangrove strata follows to plots 35

Table 4.7 Mangrove communities in 6 strata 36

Table 4.8 Tree density of mangrove communities in Hai Ha District 40

Table 4.9 Awareness of coastal people about roles of mangrove forest 46

Table 4.10.Awareness of secondary students about roles of mangrove forest 46

Table 4.11 Coastal people’s knowledge about roles of mangrove forest 47

Table 4.12 Hai Ha student’s knowledge about roles of mangrove forest 47

LIST OF FIGURES

Figure 2.1: Global mangrove forests distribution 2000 (Giri et al., 2011) Map redrawn by

UNEP/DEWA Red lines/areas indicated to mangrove forest 4

Figure 3.1: Research sites 13

Figure 3.1: Standard plots are set up on survey line 15

Figure 3.2: Plot establishment 16

Figure 4.1: Vertical profile in line 1+2 42

Figure 4.2: Cross profile in line 1+2 42

Figure 4.3: Vertical profile in line 3 43

Figure 4.4: Cross profile in line 3 43

Figure 4.5: Vertical profile in line 4+5+6 44

Figure 4.6: Cross profile in line 4+5+6 44

Chart 4.1 Percentage of species found in Hai Ha mangrove forest 24

Chart 4.2 Awareness of coastal people and secondary students about roles of mangrove forest 46

Chart 4.3 Knowledge about roles of mangrove forest of coastal people and secondary student in Hai Ha district 47

CHAPTER I INTRODUCTION

Located between sea and mainland, mangrove forests are the specially ecosystem of tropical and subtropical sea but they are sensitive with the human impact Flora and fauna in this forest have special biological characteristics to adapt with muddy, frequently saltwater environments

The existence of mangrove forests have the important meaning for environment and socioeconomic, mangrove forests not only provide valuable forest products such as: timbers, coals, woods, tannins, foods, medicines, etc but also be the detritus source to raise the local aquatic species or the species that live in estuaries and adjacent coastal Mangrove forest is the wintering habitats of migratory birds and nesting place of waterfowls (Phan Nguyen Hong, 1991) [12] Mangrove forests play important role in protecting environment, controlling climate, preventing storm, expanding the area of the continent, preventing inland encroachment of saltwater They also supply foods for raising livestock’s and breeding bees Mangrove forests help the poor coastal people to improve their life They also are the attractive ecotourism location for domestic and foreign tourists, researching and studying places of students and scientists about mangrove ecosystems However, Vietnam mangrove vegetation has being seriously degraded because of consequents of wars After wars, due to poor conditions of economy, population explosion, low awareness of resident, people exploit indiscriminately mangrove forest for materials, destroy forest to grab land for agriculture, shrimp farms, salt fields These activities make the mangrove forest areas reduce, soil degrade seriously, thousands of hectares of forest land be abandoned and not restored, biodiversity resources and fishery resources of coastal areas be impaired and environment be polluted

Recognizing the importance of mangrove forests, especially from the consequences of natural disaster in the coastal areas that lost mangrove forest, the mangrove ecosystem planting and restoring movement has being flourished in coastal areas across the country such

as program 327, Growing 5 million hectares forest program, and also some international organizations (PAM) and non-governmental organizations (SCF UK, ACTMANG, Red Cross

of Danish and Japan, etc.) cooperate with Mangrove ecosystems research centers

Hai Ha district is a border and island mountainous district, this place has 35 kilometers coastline and 8000 hectares total area of intertidal, in which 1/3 area is mangrove forest, 1/3 is aquaculture area and the rest is unused mudflats estuarine The natural mangrove forests have important role to the development of economy such as protecting dykes and shrimp ponds, improving environment and being the habitat of aquatic species with high economic value like

mangrove mud clam (LUCINA philippinarum), vạng (Geloina coason), sá sùng (Sipunculus nudus), bông thùa (Phascolosoma arcuatum) Mangrove forests are also the place to nourish

shrimps and crabs parents, abode of the baby sea animals Nevertheless, the mangrove deforestation situation for taking materials, especially deforestation for shrimp farming is occurring seriously This situation make mangrove forest areas substantial decline, up to now, only in Quang Phong commune, 90/420.36 hectares have cleared (according to the Hai Ha forestry department, 2004)[6] Besides that, after being cleared, the regeneration of flora of the natural mangrove forest is impoverished, mostly is the species of Avicenniaceae (Mắm

families) that grow purely or grow intersperse with Aegiceras corniculatum L Blanco (Sú)

These species belong to the dust type, branches close to the ground, monotonous and less floor forest, trees grow slowly and canopy slowly closed To overcome this phenomenon, there are some needed appropriate solutions as planning shrimp yard, growing more

mangrove trees that have large size like Rhizophora stylosa Giff (Đước Vòi) … Moreover,

researching to growing other addition trees that accordance with the living conditions of each region is necessary to raise the biological diversity and give back green color for Hai Ha mangrove forest Along with reforestation, the development and protection of mangroves should be more concerned Start from these reasons, in order to plant, take care of, protect and

develop mangrove forest effectively, the basic knowledge about biological classification, function as well as species composition, distribution and regeneration of the region's mangrove species is very necessary and important Although there have been many studying documents about mangrove forest but Hai Ha district still not have a research projects in species composition, distribution, biological diversity and structure of mangroves in local

And thus, from these reasons, I would like to proceed with the topic: "PLANT DIVERSITY AND STRUCTURE OF MANGROVES IN HAI HA DISTRICT, QUANG NINH PROVINCE"

CHAPTER II LITERATURE REVIEW 2.1 Mangrove forest in the world

Mangrove forests distribute mainly on the equator and 2 sides tropical hemisphere However, some species expand up to 32o22’North (Bermuda) such as: Rhizophora stylosa, Kandelia candel, and Bruguiera gymnorrhiza (Le Van Hien, 2005)

The limit of mangrove trees in South is New Zealand (38o03’South latitude) and the South of Australia (38o43’South latitude) In those areas, the species that can survive is

Avicennia marina due to the cold winter

Figure 2.1: Global mangrove forests distribution 2000 (Giri et al., 2011) Map redrawn

by UNEP/DEWA Red lines/areas indicated to mangrove forest

Following to the evaluation of Hutchings and Seanger (1987), mangrove area in the world is 15,492,000 ha There are 6,246,000 ha belong to tropical Asian region and Oceania, 5.781.000 ha belong to America regions, and 3,402,000 ha of tropical Africa (Nguyen Hoang Tri, 1999)

According to Wash (1974), the distribution of mangrove forests in the world are divided two main regions (Hoang Van Thoi, 2005)

- India-Pacific areas: including Southern Japan, Southeast Asia, India, the Red Sea coast, East Africa, Australia, New Zealand, the South Pacific Island, and Xamoa archipelago

- West Africa-Americas areas: covering the coast of Africa in the Atlantic Ocean, the Galapagos Islands, and the Americas

According to some other authors, the area between Malaysia and northern Australia is the main distribution of mangrove flora However, based on analyzing fossils, some authors said that this center is located in the southwestern and northern Australia to Papua New Guinea rather than Malaysia In Australia and Papua New Guinea have about 30 species of trees and shrubs belong to 14 families; moreover, mangrove forest also has 10 species belong

to 8 lianas, a large number of different plant species like algae, fungi, lichen, Ipomoea caprae also found in mangroves communities, but most species can live in many other

pes-communities not only in mangrove pes-communities

There are many research on mangrove forest in the world P.V.Richard has many studies in areas 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, 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 propagulesis inversely proportional to their masses When the seedlings have fixed and started growth, they usually grow poorly below the shade of tall trees (Nguyen Thi Thuy Huong, 2006)

Kasawani et al (2007) studied about for 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 the recover and management program The result shows

that Sonneratia alba is dominant species with more than 73 trees in each transect line

Suwa et al (2009) researched the structure of a subtropical mangrove forest along Okukubi River in Okinawa Island, Japan base 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

2.2 Mangrove forests in Vietnam:

Vietnam is located in tropical climate with advantages for mangrove forest development Before 1943, there are about 400,000 ha of mangrove forest areas in Vietnam, but till 1975, only left 185,877 ha due to many different reasons such as war, mining, and unsustainable management of mangrove forests

Phan Nguyen Hong (1999) published the plant species composition of Vietnam’s mangrove ecosystems includes 77 mangrove species of 2 environmental groups, and various life forms Group I has 35 mangrove species belong 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 "join" species in the mangroves and they often live in secondary forest and highland Phan Nguyen Hong also was the first man in Vietnam to mention about the geographical distribution and mangrove community’s succession in many researches Inour country’s mangrove ecosystem, there are 45 mangrove forest communities,

6 mangrove forest populations distributed in different regions

In recent years, Vietnam has many researches 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 belong to 37 genera of 24 vascular families distributed in the mangroves at study area The research has also mentioned about

some species 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 belong to 12 families; the tree participation group

includes 49 species belong to 28 families Sonneratia alba and Avicennia officinalisare

dominant tree species, and Rhizophoraforest is the largest area

Based on geographical factors, fieldwork and part of results Remote Sensing, P.N.Hong (1991, 1993) were divided into 4 Vietnam mangrove areas and 12 sub-zones:

Zone I: Northeast in the Coastal, from Mui Ngoc to Do Son

Zone II: North Delta in the Coastal, from Do Son to Lach Truong

Zone III: Central Vietnam in the Coastal, from Lach Truong to Vung Tau

Zone IV: Southern in the Coastal, from Vung Tau to Mui Nai - Ha Tien

 Zone I: Mangroves grown by the outer shielding island, the species mainly Rhizophora stylosa, Kandelia obovata, Bruguiera gymnorrhiza (L), Aegiceras corniculatum (L) Blanco, Avicennia marina Due to the air temperature in the winter cold, so the tree is small in size, only a height of about 1.5 to 7 m

 Zone II: Despite the extensive alluvial, alluvial-rich, but here empty beach, no shielding storm islands, only a few mangrove estuaries in the main tree species such as Sonneratia L , Kandelia obovata, Aegiceras corniculatum (L) Blanco, Acanthaceae Sonneratia

L relatively large size, 8-12 m tall, 15-20 cm in diameter

 Zone III: Mudflats narrow, less silt coast by steep, windy storm, forests of narrow strip just inside the estuary The trees are mostly plants: Rhizophoracaea, Bruguiera

gymnorrhiza (L.), Aegiceras corniculatum (L.) Blanco, Avicennia marina, often small trees, the branches more

 Zone IV: There are extensive mudflats, numerous sediment by the Dong Nai river system and the Mekong River system provides less wind storm so well developed mangroves, especially Ca Mau peninsula The forest has many species of trees, with a high diversity and large size

According to this division, the Hai Ha district in zone I and brought many common traits of this region but also the peculiarities of the terrain leading to mangrove vegetation has many distinctive features will be outlined in the next part

CHAPTER III STUDY GOAL, OBJECTIVES, SCOPE OF THE STUDY AND

METHODOLOGY

3.1 STUDY GOAL, OBJECTIVES

3.1.1 Goals: Assessment of biodiversity and structure of coastal mangrove forests, which proposed several solutions to contribute to better management of coastal mangroves

3.1.2 Specific Objectives:

Objective 1: Investigate the biodiversity of coastal mangrove (species diversity of

coastal mangrove) in Hai Ha districts, Quang Ninh province

Objective 2: Investigate the distribution and structure of coastal mangroves in Hai Ha

districts, Quang Ninh province

Objective 3: Propose possible solutions for sustainable mangrove management in study areas

3.2 SCOPE OF THE STUDY

3.2.1 Geographical location, topography

Hai Ha is a district of mountainous, border and island are 150 km far from Ha Long city to the north, 40 km far from Mong Cai international border gate Bordering China to the north, the border line are 22.8 km, Bordering East Sea to the south, coastline measure is 35

km, the west by Binh Lieu and Dam Ha, thw east by Mong cai town

Geographical coordinates: 210 12’ 46’’ - 1070 38’ 27’’ north latitude

1070 30’ 54’’ - 107 051’ 49’’ east longitude

The topography of the district is generally slope and strong intersect with many rivers and estuaries as Ma Ham, Ha Coi, polo, Duong Hoa and Cai Da Ban outboard of sea is covered by 2 rows of the island is The Lamb and Vinh Thuc creates a tight bay, has a low tidal systems and extensive development

3.2.2 Climate:

Like other districts of Quang Ninh province, Hai Ha district with climate regime tropical monsoon nature Hai Ha is a coastal mountainous district, the climate has moderate mountainous nature of the coastal nature, cold winter with temperatures down to 5-6 0C, often with hoarfrost

Temperature regime:

Temperature regime depends on internal tropical radiation changes over the tropics and monsoon The annual average temperature is about 22.7 0C, the average amplitude of oscillation in months from 15 - 30 0C, the highest temperature in July is 31.2 0C Because the highest amplitude of a temperature affects the growth of plants, some species of mangroves in the South are not present here, the dimension of tree is smaller than the tree in the South

The total of radiation is an important factor in the formation of climate, decisions of living and development of plants and planktons The total of average radiation of 200 kcal / cm2 / year, the highest in July is 286 kcal / cm2 (According to 2007 figures, Ho Thi Phuong, meteorological stations in Hai Ha district)

Therefore, compared to Nam Dinh province which has an annual average temperature

is 24,30C (The center of National Hydro-meteorological 2006 - 2007), Hai Ha district has an annual average temperature lower than 1,60C

Wind regime:

Formation of two monsoons are the northeast monsoon (April 10-3) and the southwest monsoon (June 4-8) The average wind speed was 2.5 m/s and reaches to maximum of 4.5 m/s

in the storm Each year has an average from 3 to 4 small big storms land on the coast

Rain regime, humidity:

Distribution of dry and rainy seasons is clearly The dry season lasts from November

to April the following year, accounting for 15-20 % of annual rainfall, the lowest rainfall is

9.3 mm in January and 11 mm in November The rainy season lasts from May 5 to 10, accounting for 80-85 % of annual rainfall The month with the highest rainfall is a June (630.7 mm) The annual average rainfall is 2630.4 mm The rainfall total of the first 6 months of the year in 2008 is 1267.5 mm and 799.8 mm in June The average humidity reaches from 85 to

90 %, the average wind speeds is 3m/s

Because the large rainfall is created such a freshwater stream relatively rich which is favorable for the growth of mangroves However, the rainy season of Quang Ninh in general and Hai Ha in particular does not coincide with seasonal fruit and germination This has

affected directly to the development of mangroves forest

3.2.3 Hydrology:

River systems are quite dense with a density 2 km/km2, the main river system is a Ha Coi river and some small rivers flow direction Northwest - Southeast Features of the river here is small, short and steep, on the river has many waterfalls and rapids, upstream is broad and downstream is narrow Estuary is heavily influenced by the tides The rivers in the district are less concentrated water flow in the rainy season The total amount of sediment and suspended solids content is low

The coastal area of Hai Ha district has 5 estuaries, in order of estuaries from north to south are Ma Ham, Ha Coi, Polo, Duong Hoa and Cai Da Ban The estuaries are funnel-shaped

Tide: In a month there is an intensity water, the vibration amplitude of wave from 0.5

to 1m This is also the area with the greatest height of tidal coastal range in Vietnam, can reach to 4 - 5m Wave regime depends on seasonal wind regimes and shape of regional topography However, due to coastal topography of coastal areas and estuaries is relatively tight so it is less affected by waves of Gulf of Tonkin, the internal waves formed is relatively weak, no more than 1 meter in a storm This is also facilitates in the distribution and growth

of mangrove trees

3.2.4 Salinity:

The highest salinity on winter is 30-31 ‰ because it is less rain on this period Salinity

is lowest on summer with 10-15 ‰ In the estuary area flow into the bay, the lowest salinity is possible down to 2-4 ‰ Salinity in Thai Binh is lower, in the flood season from 9-17 ‰ and the dry season from 23-30 ‰ The salinity is relatively high to be suitable with the growth

and development of salt-tolerant species such as: Avicennia marina (Mắm), Aegiceras corniculatum (Sú)…

Because of the different backgrounds led to the flora in these two regions are also different, the flora in Quang Phong, Tien Toi, Duong Hoa communes is rich and more developed in the Quang Thanh, Quang Thang Quang Minh communes (Data on the "Draft plan of aquaculture in Hai Ha District in period 2006 to 2010 '', 2005)) [6]

Hai Ha district has six coastal communes following the sections from north to south respectively: Quang Thanh, Quang Thang, Quang Minh, Quang Phong, Duong Hoa, Tien Toi

Figure 3.1: Research sites

The Red-crossed marks show research sites

The total area of tidal ground which has salt-marsh vegetation of the district is 1046, shown in the following table:

Table 3.1: The area of tidal ground has salt-marsh vegetation in Hai Ha district

Community Quang

Thanh

Quang Thang

Quang Minh

Quang Phong

Đuong Hoa Tien Toi

(According to the report "Current status of mangrove forests and forest land in Hai Ha district on 2015'' of the Agriculture and Pisciculture department in Hai Ha district)

3.3 CONTENTS AND METHODOLOGY

3.3.1 Research Content

Objective 1: To investigate the biodiversity of coastal mangrove (species diversity of

coastal mangrove) in Hai Ha districs – Quang Ninh province

- Investigate and assess the diversity of species, communities of mangrove forests

- Determine of species composition and assess species diversity of mangroves

Objective 2: To investigation on the status of distribution and structure of coastal

mangroves in Hai Ha districs – Quang Ninh province

- Research some of the ecological conditions in mangrove forests areas

- Research the status and distribution of mangrove forests in Hai Ha District - Quang Ninh Province: Determine areas of mangrove forests, determine the area of distribution and species composition of vegetation in the forest area

- Research the structures of mangroves: investigate and determine species composition, structure mangroves in the study area

Objective 3: This objective proposes possible solutions for sustainable mangrove

management in study areas

- Find out the impact of local people to mangroves

- Investigate and interview the manager to know the management mechanisms of mangroves at the local

- Recovery solutions of mangroves area

- Sustainable management solutions associated with economic development

- Protection measures and sustainable development of mangroves

(from the dike to sea) In each commune have mangrove forest, we set up by lines from the dike to sea about 3 lines for 6 communes (Quang Thanh, Quang Phong, Quang Thang, Quang

Minh, Duong Hoa, Tien Toi)

Figure 3.1: Standard plots are set up on survey line

 Set up standard plots on survey line:

On each survey line, I selected 3 typical locations in the study area and distance from dike to sea is about 50m, 150m and 250m to set up 3 plots (Plot 01; Plot 02; Plot 03) and each plot has an area with 400 m2 (20m x 20m), each big plot had 5 sub-plots (2m x 2m) 4 plots at the corners and one plot at the center of plot 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 I set up about 18 plots in the study area

Figure 3.2: Plot establishment

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, and date of investigation, investigator and 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

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 drawn solid 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 analysis and assess scientific name

 Interview method, surveys households, local governments:

To assess the impacts of local people on the mangrove forest, we use interview methods, interviewed by the questionnaire for the local people, local officers, households, farmer, fisher, in the study area to find out about regulations, institutional resource management

Investigate, collected on the number and severity of exploitation of natural resources, ecological characteristics of some species

The type of management, exploitation and use of natural resources in the local as well

as the development orientation

3.3.2.2 Data analysis methods:

Statistical table about components and species compositions (following to Nguyen

Nghia Thin, 2007)

Assessing scientific name: by the method of morphological comparisons between specimens collected with documents related to plant such: Vegetation of Vietnam (Pham

Hoang Ho, 1999-2000), Forest tree name of Vietnam (Vu Van Dung, 1996), Plants in

mongroves of Vietnam (Nguyen Hoang Tri, 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 Nghia Thin 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, improvement sand area less tidal and coastal shrimp farms, road and sea dike based on

separation of Phan Ke Loc and Nguyen Tien Hiep (1998)

Analyze data by excel 7.0 software

- 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

CHAPTER IV RESULTS AND DISCUSSION 4.1 DIVERSITY OF MANGROVE FORESTS IN COASTAL AREA HAI HA DISTRICT, QUANG NINH PROVINCE

4.1.1 List of mangroves in the study area

After carrying out field research, collecting and analyzing samples depending on materials and helps of some experts, we have the list of Species in 6 coastal communes of Hai

Ha district, Quang Ninh province as follow:

(Names of species are arranged in alphabetical order and according to Phylum; Family; Latin name; respectively)

Table 4.1 List of mangroves in 6 coastal communes in Hai Ha district, Quang Ninh

province

No Scientific Name

(Phylum/Family/Latin Name)

Vietnamese Name (Phylum/Family /Common Name)

Species Life

forms Habitat Distribution

CLASS1.DICOTYLEDONEAE Lớp Hai lá mầm

7 Plucchea indica (L.) Lees Cúc tần - H 4,5 A

Fam 10 Chenopodiaceae Họ Rau muối

Fam 12 Euphorbiaceae Họ Thầu dầu

18 Scaevula taccada (Gaentn.)

20 Thespesia populnea (L.) Soland Tra lâm vồ, Tra

Fam 17 Rhizophoraceae Họ Đước

Fam 19 Verbenaceae Họ Cỏ roi ngựa

Fam 22 Arecaceae = Palmeae Họ Dừa

35 Eleocharis dulcis ( Burm.f)

Fam 24 Flagellariaceae Họ Mây nước

2 Areas where are usually flooded with tide

3 High land areas or along the bank of salt-marshes where are rarely affected by tide

4 High land areas in side of dykes where are affected by salty air or flood tides

5 Areas along the bank of rivers where are usually flooded with tide

6 In some aquaculture ponds

Distribution

QM : Quang Minh commune

QT : Quang Thanh commune

QP : Quang Phong commune

TT : Tien Toi commune

QTh: Quang Thang commune

DH: Duong Hoa commune

A: All of communes

Initially, we just surveyed initially 2-3 strata from the dyke to coast in Hai Ha district After collecting, surveying and analyzing plant samples, we found 41 species belonging to 26 families (Detail in Table 4.1.1) With species in community planting casuarina, we did not have condition to identify In total identified species, angiospermae phylum has 28 species in dicotyledoneae class (68.3%) and 12 species in monocotyledoneae class (29.3%) Pteridophyta has only 1 species (2.4%) From the results, we can realize that number of mangrove species in Hai Ha district is abundant in comparision with Quang Ninh province There are 36 species in 24 families (Ha Long Bay Management Board, 1997), (According to Tran Thi Binh, 2002)

Numbers of species and percentage of species found in Hai Ha Mangrove forest are presented on the table below:

Table 4.2 Numbers of species in phyla and classes found in Hai Ha mangrove forest

Chart 4.1 Percentage of species found in Hai Ha mangrove forest

Among the species found are 10 main mangrove species and 31 species living in mangrove forest Because we did not have enough time, we have not researched some species

in interior area scattering along the shoreline

Main mangrove species are not big because of the high temperature amplitude and

ground contains mostly gravels and sands Dominant species are Avicennia marina (Mắm) or Aegiceras corniculatum (Sú) because they are pioneer in the bog, moreover they can adapt to

high salinity better

According to the division of mangrove forests into areas and sub-areas, Hai Ha district belongs to Area I, in Sub-area 1 from Mong Cai city to Cua Ong provice (P.N.Hong, 1999)

The flora in Hai Ha district has common characteristics of this area That is Avicennia marina (Mắm Biển) community where there are only pure species or both Aegiceras corniculatum

(Sú) living in alluvia ground In some medium level tidelands, there are mixed communities

involving Rhizophora stylosa Giff (Đước Vòi), Bruguiera gymnorrhiza L.( Vẹt dù) species and mostly Avicennia marina and Aegiceras corniculatum species In some high level tidelands, there are dominant communities including Excoecaria agallocha L (Giá),

2.4%

68.3%

29.3%

Percentage of species found

in Hai Ha mangrove forest

PTERIDOPHYTA Dicotyledoneae Monocotyledoneae

Lumnitzera racemosa Gaud (Cóc Vàng) On bank of swamps, there are mostly Hibiscus tiliaceus L (Tra), Thespesia populnea L Soland (Tra Biển), Clerodendron inerme L (Vạng Hôi), Scaevula taccada Gaentn Robx (Hếp)

In 6 communes we research, there are estuaries: Ma Ham, Ha Coi, Po Lo, Duong Hoa and Cai Ba Dan River These are small rivers having fulnel-shaped river mouths and high slope On some alluvial grounds, there are many gravel and rocks, and less silt There are much water and silt only in flood seasons so the flora in here is poorer than in other regions For example: in Ba Lat River Mouth, Tien Hai district, Thai Binh province, soils are mostly

silt so the flora is very abundant Dominant plants are Kandelia cande (Trang), Aegiceras corniculatum (Sú) and Sonneratia caseolaris (Bần Chua) species (P.N.Hong et al., 2004) The flora in estuaries of Hai Ha are mostly Sporobolus virginicus (L.) Keenth (Cỏ caý), Acrostichum aureum (Ráng) There are very few pioneer mangrove plant species like Mam

Su Especially there are no brackish water plants that are popular in some other river mouths

of Thai Binh, Nam Dinh like Sonneratia caseolaris (Bần Chua) and Sciphiphora hidrophirallacea (Côi)

Through surveying, we realized that Deris heptaphilla (Dây cốc kèn) is less

developed We only found this species in Quang Phong They climb and need the support of

other plants like Acrostichum aureum (Ráng) near the dyke

The most abundant flora is in Quang Phong and Tien Toi communes where there are mostly humus and clay soils Some areas have not been deforested Especially, we found

Flagellaria indica (Mây nước) in Tien Toi commune and could not find in other communes Where we found Flagellaria indica (Mây nước) is low-lying land and flooded but is not usually flooded by tide These plants only gather in Tien Toi dike edge Excoecaria agallocha

L (Giá) and Thespesia populnea L (Tra) Soland) grow rather high and verdant luxuriant There are some trees having height 6-7m Association of Suaeda maritima (L.) Dum (Muối

biển), Acanthus ilicifolius L (Ô rô lá nhỏ), Flagellaria indica (Mây nước), Excoecaria agallocha L (Giá) grow in a jumble There are some Suaeda maritima (L.) Dum (Muối biển)

plants having height 1m

After researching and basing on Table 4.1, we divided life forms of plants in mangrove forest into 8 forms (Numbers and percentages are shown on Table 4.3)

Table 4.3 Life forms of mangrove plants in Hai Ha district, Quang ninh provice

Woody plant species make up 29.2% (a major part is some main mangrove species

like, Rhizophora stylosa Giff (Đước vòi), Bruguiera gymnorrhiza L (Vẹt dù) and others living in mangrove like Excoecaria agallocha L (Giá), Hibiscus tiliaceus L (Tra làm chiếu), Thespesia populnea (L.) Soland (Tra làm vó) Size of trunk here is small because of

temperature amplitude in seasons is relatively high, the winter is cold and percentage of organic silt is low Because of high salinity, growing and regenerating abilities are still low Our research is also conformable with the research of P.N.Hong, 1991

Shrub species make up 9.8%; major species belong to Goodeniaceae (Hếp) families

They often grow along the bank of shrimp ponds and estuaries

Herb species is 36.6% In there, there are mostly species are Poaceae (Họ Lúa) and Cyperaceae (Họ Cói) families They grow in intertidal banks and along the bank of bogs

We found only 4 climber species and 1 fern species (have the lowest percentage of total found species)

In summary, mangrove species in Hai Ha district are relatively diversified but still poor in comparison with the whole Quang Ninh province and other provinces like Thai Binh, Nam Dinh Because salinity is very high (21-22%), in dry season it reaches 32%, while mangrove forests develop in areas having salinity about 10-25%, size and numbers of species also decrease when the salinity is high (40-80%) (Blasco, 1984) There have not been protection and development though there are some afforest campaigns in Hai Ha district, but

it does not bring high effects

4.1.2 Value of mangrove forest

If we protect and develop mangrove forest, it will bring many great economic and environmental values for Hai Ha district

Mangrove forest supplies timbers, building materials and art objects Wood of some

species such as Rhizophora stylosa Giff (Đước vòi), Bruguiera gymnorrhiza L (Vẹt dù) are

very hard and they are used for building materials like post, plank, beam and furniture…

Low-quality woods of some species like Avicennia marina (Mắm), Excoecaria agallocha L (Giá) are used as plywood; leaves of Nypa fruticans (Dừa nước) are used as partition or roof Mangrove forest provides industrial products: Woods of Excoecaria agallocha L (Giá), Avicennia marina (Mắm) are soft and white so used for producing pulp Woods of Aegiceras corniculatum (Sú) are smooth and have red color so used for sculpting statues (P.N.Hong et al., 2007) There are some Bruguiera gymnorrhiza L (Vẹt dù) having height 3m and diameter

12cm in Hai Ha district However, the quantity is very low There should be solutions to develop mangrove plants in here so that we can exploit values of this species

Mangrove forest supplies tannin: Tannin is extracted from the barks of Rhizophora stylosa Giff (Đước vòi), Bruguiera gymnorrhiza L (Vẹt dù), Aegiceras corniculatum (Sú)

and used for dyeing cloth, net and tanning leather Buds of Rhizophora stylosa Giff (Đước

vòi) species plants have much tannin Formerly coastal people in Hai Ha district exploited tannin from barks and buds of these plants to making diarrhea medicine and tanning net

Mangrove forest supplies fuels People can use falling branches as firewood

Rhizophora stylosa Giff (Đước vòi) and Bruguiera gymnorrhiza L (Vẹt dù) charcoals have

high heat, can keep fire burning long and liked by citizens and international market

Mangrove forest supplies food, drink, and medicine: Most of mangrove leaves is

protein-rich cattle-feed Fruit of Avicennia marina (Mắm), is protein-rich and used for

foodstuff for fish Many mangrove trees are valuable popular medicinal plants Nowadays, we have found 15 mangrove species that can be used for medicine (P.N.Hong et al., 2007) Barks

and leaves of Aegiceras corniculatum (Sú) are used for making gargle to treat goiter Trunks and leaves of Acrostichum aureum (Ráng) are used for treating helminthiasis and styptic; dry

stems are used for making broom and baskets… (Nguyen Dinh Quy, 2002) In the past, people in Hai Ha used fruits of Mam to preserving in salt for food and used fresh fruits to feed fish, but now we do not see that anymore because the source of food is abundant

Mangrove forest supplies organic matters (falling and decomposing branches, leaves, fruits ) as food for some animals living in the intertidal zone such as shrimp, crab So inshore fishing depends on mangrove forest very much It means the more of mangrove forest

we lose, the less of seafood we have (P.N.Hong et al., 2007)

Mangrove forest not only supplies sources of economic incomes, but also has some direct benefits like regulating climate; fighting against erosion; protecting shoreline, riverside; avoiding storm;… With mangrove forest in estuaries where are effected by wind and wave, these benefits have significant importance (P.N.Hong et al., 2007) Hai Ha district is located

in the airtight gulf region and guarded outside by Cai Chien and Vinh Thuc islands, so it is rarely affected by hurricanes This condition combines with the uninterrupted and verdant

luxuriant mangrove forest belt will help Hai Ha to become a safe area about ecology, avoiding natural disaster, and stable for strategy of economic development in the future

Hai Ha mangrove forest plays an important part in the strategy of economic development and coastal environment protection However, local people have not been aware

of protecting forest because they have not realized fully the important roles of mangrove forest and economic values of mangrove plants in Hai Ha district Through surveying and studying uses and values of mangrove plants in Hai Ha district, we found some common values (Details are shown on the table below)

Table 4.4 Values of mangrove species in Hai Ha district

No Scientific Name

(Phylum/Family/Latin Name

Vietnamese Name (Phylum/Family /Common Name)

Values

Medicine Wood,

firewood Food

Cattle -feed

Protect dyke, prevent wave, wind

Ornament

Honey, Fibre for handic raft

Ta nni

n

Green manure, improve soil

17 Deris heptaphilla (L.) Merr Cốc kèn + + +