Summary of biological doctoral thesis: Research on mangrove vegetation which have biological activities in Xuan Thuy National Park and propose sustainable usage

This dissertation contributed to implement data on the diversification of vascular plants, structure, biomass of some typical mangrove vegetation communities, chemical compositions, and biological activities of mangrove vegetation in Xuan Thuy National Park.

MINISTRY OF EDUCATION AND TRAINING VIETNAM ACADEMY OF

SCIENCE AND TECHNOLOGY

GRADUATE UNIVERSITY OF SCIENCE AND TECHNOLOGY

-

PHAN THI THANH HUONG

RESEARCH ON MANGROVE VEGETATION WHICH HAVE BIOLOGICAL ACTIVITIES IN XUAN THUY NATIONAL PARK

AND PROPOSE SUSTAINABLE USAGE

Major: Botany Code : 9 42 01 11

SUMMARY OF BIOLOGICAL DOCTORAL THESIS

HANOI - 2018

This thesis was fulfilled at Graduate University of Science and Technology

Supervisor 1: Assoc.Prof Dr Tran Huy Thai

Supervisor 2: Dr Nguyen Hoai Nam

Reviewer 1: Assoc.Prof Dr Nguyen Trung Thanh

Reviewer 2: Assoc.Prof Dr Trinh Thi Thuy

Reviewer 3: Assoc.Prof Dr Nguyen Khac Khoi

The thesis will be defended in the Graduate University of Science and Technology (GUST) council at Vietnam Academy of Science and Technology (VAST) at …… on… 2018

This thesis may be found at:

- The library of GUST

- National Library of Vietnam

INTRODUCTION

1 The urgency of this dissertation

Mangroves are important to not only ecology but also socio-economic Mangroves are considered as a center of tropical marine biology, one of the world’s most biodiversity and genetic ecosystems About 90% of marine organisms live in mangroves, and 80% of the

world’s fisheries depend on mangroves (S Sandilyan, 2012) However, the mangrove

ecosystem is vulnerable to human impacts and climate change There have been several hitherto report that mangroves in the world are severely degraded (FAO, 2007) In an effort

to protect this particularly valuable ecosystem, scientists have been researching in a variety

of aspects in order to exploit, converse and develop these resources in a scientific and effective way

Vietnam, with more than 3,000 km of coastline, has a rich mangrove forest system stretching from north to south Mangroves not only act as a major role in ensuring the livelihoods of the coastal residential but also play an extremely important role in ensuring environmentalism, reducing nature’s impacts and overcoming the phenomena of rising sea level, saline intrusion, etc

Xuan Thuy National Park, which belongs to the Northern mangrove system, is located

in the southeast of Giao Thuy district, Nam Dinh province, at the Ba Lat estuary of the Red River According to previously punlished documents, the total area of the park is approximately 7,100 hectares, including 3,100 hectares of land and roughly 4,000 hectares of mangrove forest Xuan Thuy National Park is the 50th Ramsar Site of the World, the first of Southeast Asian and the only of Vietnam from 1989 to 2005 In accordance with the report

of Xuan Thuy National Park, it is preserving the precious ecological value, such as thousands

of hectares of mangroves, rich aquatic resources including algae which have economic value

The resources of Xuan Thuy National Park are likely to exploit bioactive substances, including: 1) Mangroves species; 2) Mollusca; 3) Botany that live in mangrove conditions; 4) Microalgae and microorganisms of mangroves In particular, mangrove plants play the central role of the mangrove ecosystem This biological resource has not been researched, exploited and used effectively, along with the risk of recession due to the impact of emphatic climate change and human activities However, nowadays, there are insubstantial and comprehensive studies on mangrove plant in Xuan Thuy National Park towards biological activity have shown

To contribute to researches related to the mangrove system, the Ph.D student

conducted a research project “Research on mangrove vegetation which have biological

activities in Xuan Thuy National Park and propose sustainable usage”

2 The meaning of dissertation topic

 Scientific significance

This dissertation contributed to implement data on the diversification of vascular plants, structure, biomass of some typical mangrove vegetation communities, chemical compositions, and biological activities of mangrove vegetation in Xuan Thuy National Park

 Practical significance

Based on the results of the research, the thesis has selected mangrove species with biological activity and proposed sustainable use of some valuable medicinal species in order

to conserve and develop mangrove plants in Xuan Thuy National Park

3 Structure of the dissertation

The dissertation consists of 146 pages, including: Introduction (2 pages); Chapter 1: Overview (28 pages); Chapter 2: Subjects, scope, content and methods (14 pages); Chapter 3: Research result and discussion (83 pages); Chapter 4: Conclusion and request (3 pages); New contributions of the thesis (1 page); List of published works (1 page); Reference (14 pages)

CHAPTER 1 OVERVIEW

1.1 Mangrove definition

The term ‘mangrove’ cannot be definite in the exact way Saeger’s definition of mangrove is a type of tall plant (trees, shrubs, herbs or ferns) which dominate in semi-tropical coastal tide, subtropical, showing a distinct level of tolerance to anaerobic conditions and high

salinity, and blume can live in marine dispersal condition (P Saenger, 2002)

1.2 Geographic distribution, mangrove area

1.2.1 Mangrove area and distribution in the world

Mangrove is distributed mainly in the equatorial and tropical area of two hemispheres (between latitudes 23oN and 23oS), at coastline, island chains, warm Gulf Stream spreading offset from the abundant mangrove to cooler areas Mangrove in the world is distributed in

124 countries and regions Mangrove accounts for approximately 1 % of the world’s forest area and appear in about 75% of the tropical coasts of the world (P Saenger, 2002)

1.2.2 Mangrove area and distribution in Vietnam

According to Phan Nguyen Hong et al (1999), mangroves in Vietnam are divided into four zones and 12 sub-zones: Zone I: Northeast Coast, from Ngoc headland to Do Son headland; Zone II: Northern Delta Coast, from Do Son headland to Lac Truong headland; Zone III: Central Coast, from Lach Truong headland to Vung Tau headland, Zone IV: South Coast, from Vung Tau headland to Nai headland, Ha Tien

1.3 Value, role of mangrove

Mangroves are important ecosystems that provide a variety of goods and services to the coastal citizens The profit of mangrove includes timber and non-timber forest products, aquatic product resources, biofiltration, coastal protection, carbon storage and absorption, recreation and ecotourism

1.4 Mangrove plants

1.4.1 Mangrove plants diversity in the world

The total number of species of vegetation in the world is 23 genera and 53 species belonging to 16 families According to Saenger et al (1983), the total number of mangrove species is 60 species The exact number of mangroves in the world so far has been debated and discussed among taxonomists The official number of mangrove vegetative species ranging from 50 to 70 following the different classification systems

1.4.2 Mangrove plants diversity in Vietnam

It can be said Phan Nguyen Hong, who has many monographs, articles on mangrove has been published, is a leading author in the study of mangroves in Vietnam In 1993, Phan Nguyen Hong published the list of 77 species of mangroves in two groups divided into different environmental and life forms: Group 1, referred to as true mangrove, has 35 species belonging to 20 genera of 16 families; Group 2, has 42 species belonging to 36 genera of 28 families, including species live in mangrove, which usually grow in secondary and planted forests on high ground Nowadays, there are 69 mangrove species in the South, and 34 species

1.6 Research on the chemistry and biological activity of mangrove plants

1.6.1 Research on the chemistry of mangrove plants

1.6.1.1 Research situation in the world

These days, there are more than 40 plant species have been chemically studied, 349 compounds have been isolated from mangrove plants and 200 compounds from semi-mangrove plants, in which 200 secondary metabolite compounds are reported to be present in only real mangrove species, and 80 compounds are found only in semi-mangrove plants, LP Jayatissa et al., 2006

1.6.1.2 Research situation in Vietnam

In Vietnam, the research on the chemical composition of mangrove species is quite poor and not really comprehensive Nguyen Thi Hoai Thu et al studied the chemical

composition of Sonneratia alba collected in Can Gio Mangrove The results showed that six compounds are isolated from petroleum ether fraction of leaves of Sonneratia alba including oleanolic acid, betulin, betulinic acid, alphitolic acid, methyl gallate and 5- hydroxymethylfurfural (Nguyen Thi Hoai Thu et al 2011)

1.6.2 Research on biological activity of mangrove plants

1.6.2.1 Researches in the world

Mangrove forests are rich in chemical compounds such as steroids, triterpenes, saponins, flavonoids, alkaloids and tannins Extracts from mangrove species are thought to have a variety of medicinal properties

Studies on biological activity have shown that mangrove plant species have antimicrobial activity, antioxidant, cytotoxic, anti-cancer, anti-fungal, antimalarial and antimicrobial activity assay

1.6.2.2 Researches in Vietnam

As well as studies on the chemical composition, studies on the biological activity of mangrove species in Vietnam are few and far from comprehensive

Pham Van Ngot et al studied on the antimicrobial activity of some mangrove species

in Can Gio Mangrove Biosphere Reserve The results show that the methanol fraction from

10 species of mangrove: S alba, D trifoliate, L racemosa, R apiculata, R mucronata,

Pluchea indica (L.) Lees., Dolichandrone spathacea (L.f.) Seem., Wedelia biflora (L.) DC.,

B gymnorhiza, X granatum are resistant to pathogens such as Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa (Pham Van Ngot et al., 2015)

CHAPTER 2 SUBJECTS, CONTENTS AND RESEARCH METHODS

2.1 Subjects and research scope

The study subjects are tracheophyta vascular plants and some mangrove floristic composition conditions in high tide and sand dunes in the core and buffer zone of Xuan Thuy National Park Plant species in agricultural ecosystem, artificial ecosystems are not mentioned

+ Diversity in vascular plants taxon-level at Xuan Thuy National Park

+ Diversity of life forms, botanical geography

+ Assess value in use of plants species

+ Rare species plants have conservation value

- Research on structure, biomass from a few feature plants communities in Xuan Thuy National Park

- Sampling, bioactivity screening of some mangrove for the next study

- Research on chemical constituents and biological activity of Sonneratia caseolaris (L.) Engl and Rhizophora stylosa Griff from Xuan Thuy National Park

- Propose sustainable usage on mangrove vegetation which have biological activities

in Xuan Thuy National Park

2.3 Research methods

2.3.1 Research methods of diversity in vascular plants

2.3.1.1 Methods of inheritance

2.3.1.2 Methods of plants investigation by routes

Research methods of diversity in plants using scientific documents of N.N.Thin (1997, 2004

…) combined results from the study of the world’s research

2.3.1.3 Analysis of collected information and data

a) Definition of scientific name, establish plants species list

Definition of scientific name: The scientific names of mangrove species was determined by morphological comparison methods The main documents used are FAO (1994), Vietnamese Herbs (P.H.Ho, 1999-2000), List of Vietnamese Plants (Nguyen Hoang Tri, 1996)

Establish plants species list based on the system opinion A.L.Takhtazan (1973), N.T.Ban (2003, 2005) for the branches and classes Families and species in families are arranged in alphabetical order of the scientific names (Brummit, 1992)

b) Diversity assessment in plants taxon-level

Assessment of diversity in plants at the level of branches and classes: Statistics of number of families, genera, species with each branches, classes, families and genera

Identify genera index (species average number of a genera), families index (species average number of a families), and genera/families index as the average genera per families

Assess the diversity in a species in families and genera: Statistics of 10 families and

10 genera to determine the diversity in a species in families and genera

c) Diversity assessment in plant life-form

The plant life-form is determined by Raunkiaer system (1934)

d) Diversity assessment in botanical geography

Based on the distribution of species in the world and Vietnam to identify botanical geography factors according to Pocs Tamas, 1965 and Le Tran Chan, 1999

e) Assessment value in use of plants species

The value in use of plant species is determined by the following key documents: Vietnam Forest Tree Name (Ministry of agriculture and rural development, 2000), 1900 useful plant species in Vietnam (T.D Ly, 1993), Useful plants in Vietnam (V.V Chi & Tran Hop, 1999) Vietnamese medicinal plants and herbs (D.T Loi, 1995), Dictionary of medicinal plants in Vietnam (V.V Chi, 2012), Vietnam Plant Resources (T.M Hoi, 2013)… And based

on the study that gathered by local usage experiences

f) Assessment of the conservation value of plants

Vietnam Red Book (2007), Decree 32/2006 / ND-CP (2006) of the Government

2.3.2 Research methods of the structure of mangrove plants communities

2.3.2.1 Field research methods

Methods of vegetation research based on the method of plants research by Nguyen Nghia Thin (2007)

2.3.2.2 Methods of analysis information, data processing

Summarize all data collected from the phase report, measurement at plot to calculate, analyze and process data Data is processed and analyzed by Microsoft Excel 2007

Determine biomass of species in plant communities according to the formula of Komiyama (2005)

2.2.3 Methods of chemical research and biological activity

2.3.3.1 Methods of isolation of compounds

a) Thin layer chromatography (TLC)

b) Preparative thin layer chromatography (Prep TLC)

c) Column chromatography (CC)

2.3.3.2 Methods of determining the structure of compounds

The general method for determining the chemical structure of compounds is to combine the determination of physical properties with modern spectroscopic methods including:

a) Mass spectrometry (ESI-MS)

b) Nuclear Magnetic Resonance Spectrum (NMR)

c) Melting point (Mp)

2.3.3.3 Methods of biological activity research

a) Evaluation of antimicrobial activity assay

Antimicrobial activity assay: evaluatation of the antibiotic activity of the fractions proceeded on 96 well microtiter plates by methods Vander Bergher and Vlietlinck (1991) and McKane & Kandel (1996)

b) Evaluation of cytotoxic activity assay

The in vitro cytotoxicity assay was approved by the National Cancer Institute (NCI)

as the standard cytotoxicity test for screening, detecting compounds that inhibit growth or kill cancer cells This test is performed according to the method of Monks (1991)

CHAPTER 3 RESEARCH RESULTS AND DISCUSSION 3.1 Diversity in vascular plants at Xuan Thuy National Park

3.1.1 Definition of scientific name, establish plants species list

Based on the collected samples, the scientific name has been determined and established vascular plants species list According to the results, Xuan Thuy National Park has recorded

116 species (including mangrove plants, species involved in mangroves, species from inland and adapted to Xuan Thuy National Park) belonging to 101 genera, 42 families of

include 32 families, 73 genera, 112 species, Liliopsida include 5 families, 21 genera, 26

species of vascular plants Xuan Thuy National Park has 18 mangrove plants, 88 species involved in mangroves, 10 species from coastal inland

3.1.2 Diversity in plants in the Xuan Thuy National Park

3.1.2.1 Diversity in branches

Diversity in branches at Xuan Thuy National Park has only 2 branches and very

different in number of species Magnoliophyta has 109 species, 93.97% of total species; 94

genera, 93.07% of total genera and 37 families, 88.1% of total families in the study area

Families and genera of Magnoliophyta have a high percentage compared to the rest

Polypodiophyta, only 7 species, has 6.03% of total species; 7 genera, 6.93% of total genera

and 5 families, 11.9% of total families in the study area

Diversity index of families, genera and average diversity index genera and families:

- Diversity index of families is 2.76

- Diversity index of genera is 1.15

- Average diversity index genera and families is 2.4

3.1.2.2 Diversity in families

Of the 42 vascular plants branches at Xuan Thuy National Park, 20 families has only one species; 10 families has 2 species and 2 families has 3 species There are 32 families has the least number of species The 10 most diverse families are from 4 to 15 species, including one family have 15 species (Poaceae), followed by a family of 14 species (Asteraceae), a family of 9 species (Verbenaceae), a family of 6 species (Cyperaceae), two families of five species (Rhizophoraceae, Malvaceae) and four families of four species (Amaranthaceae, Euphorbiaceae, Fabaceae, Solanaceae)

3.1.2.3 Diversity in genera

Plants at Xuan Thuy National Park has 10 large families (9.9%) with 24 species (23.76%) The most abundant species are Cyperus with 4 species (3.96%); Bruguiera and Sonneratia has 3 species (2.97%); the remaining 7 genera are Acanthus, Achyranthes, Pluchea, Solanum, Vitex, Pandanus and Paspalum has 2 species (1.98%)

3.1.3 Diversity of life forms

In Xuan Thuy National Park, 115 species (99.13% of total species) have been identified, one species has not been identified Of the species identified, the upper shoot group (Ph) was dominant with 66 species (55.65%); followed by group of trees near the soil (Ch) has 17 species (14.78%), group of trees a year (Th) has 17 species (14.78%); group of hidden-shot tree (Cr) has 9 species (7.82%) and semi-hollowed tree (Hm) has 8 species (6.95%) were the lowest

Set up a live spectrum for plants at Xuan Thuy National Park as follows:

SB = 55.65 Ph + 14.78 Ch + 6.95 Hm + 7.82 Cr + 14.78 Th

So the upper shoot group (Ph) has the largest number of species, playing a dominant role in comparison to other life forms Group Ph spectrum as follows:

Ph = 7.25 Mg + 10.93 Me + 4.69 Mi + 46.87 Na + 12.5 Lp + 18.75 Hp

3.1.4 Diversity of botanical geography

Botanical geography factors of 113 plant species (97.41%) have been identified, while

3 species have not identified (2.59%) Among the botanical geography factors of Xuan Thuy National Park, the Asia tropical factors is the highest proportion (32.76%); followed by new-tropical and inter-tropical factors has 16.38%; Indochina factor has 7.76%; Hainan - Taiwan

- Philippines has the lowest rate of only 1 species (0.86%)

3.1.5 Value in use of plants species

Of the 116 species of plants in Xuan Thuy National Park, 108 species have been used (93.1%) and the remaining 8 species (6.9%) have not been identified

Number of medicinal plants (THU) with 101 turns (46.76%), accounting for the most; followed by eatable tree (DNA) with 32 turns (13.42%), other uses such as fuel, land improvement tree (CDK) has 18 turns (8.33%); tree for the oil (CTD) and tree for tanin, tobacco (TAN) has 16 turns (7.4%); ornamental plants (CAN) has 9 turns (4.17%); wood tree (LGO) and tree for fiber (SOI) have 7 turns (3.24%), poisonous plants (DOC) have 6 turns (2.8%); fodder plants (AGS) has 5 turns (2.31%); the lowest is handicraft plants (DTC) only two (0.92%)

3.1.6 Rare species plants have conservation value

In Xuan Thuy National Park have only one rare, threatened, valuable species (0.86%)

is Scirpus kimsonnensis N.K Khoi, both is endemic to Vietnam in the coastal waters, and

listed in the Vietnam Red Book (2007) as threatened with extinction This species is valuable for cattle feed

3.2 Research on structure, biomass of some typical mangrove communities in Xuan Thuy National Park

3.2.1 Classification of carpet mangroves in Xuan Thuy National Park

According to T.V Trung (1978) and N.N Thin (2004), typical carpet mangroves in Xuan Thuy National Park is in the system: group of plant types at altitude less than 700 m in

the North and less than 1000 m in the South; closed forest types; tropical evergreen forest types; forest on mangrove land types This carpet type have 6 communities:

- The K candel community

- The K candel, S caseolaris, A corniculata, R stylosa community

- The mangrove community of K candel, A corniculata participate but have not

advantage

- The mangrove community of A corniculata, K candel participate but have not

advantage

- The A corniculata, S caseolaris, K candel community

- The community of A corniculata, S caseolaris, K candel participate in low density

3.2.2 Describe the structure and biomass identification of six typical mangrove communities in Xuan Thuy National Park

3.2.2.1 The K candel community (Plot 01)

 Describe the structure:

This type of community is located in the core zone of the park, Con Ngan area To study this type of community, we installed a plot at coordinates N: 20013’12.8”, E:

106032’57.1”, the plot dimension was 20 x 20 m (400 m2)

Plot 01 have only K candel 20 years old was planted in 1997

Stratification: The canopy stage has only a single stage with K candel, the height of the tops is relatively equal 4 - 4.2 m Shrubs and regenerated trees only have regenerated K

candel has height less than 10 cm

The number of K candel in phase 2 (4/2015) decreased sharply compared to phase 1 (6/2014) (from 770 trees to 375 trees) because 395 K candel trees died Phase 3 (4/2016), the number of dead K candel has decreased significantly, only 24 more, the density of trees decreased to 8,775 trees/ha Most of the K candel trees in this plot are leafy and dry Death

trees occur in small groups or scattered The dead trees have been decayed, broken, fallen

The sharp decline in the density of K candel in this plot was identified by storms and poor soil At the end of the study (4/2016), K candel in this plot had a density of 8,775 trees/ha

Groups of trees with the diameter of 3.1 - 3.5 cm and 3.6 - 4 cm have 60-70%, in addition to the distance between the smallest diameter trees (2 cm) and the largest diameter

trees (4.5 cm) is not too far It shows K candel in this plot have relatively equal diameters

The number of regenerated K candel is poor, scattered in this plot, height from 10 to

20 cm, normal growth, but the potentiality to grow into mature trees is not very good because the ground in this area is bad, subsidence, low regeneration density

 Biomass

Biomass of wood trees in plot 01 is declining At the end of the study, the average biomass of wood mangroves in plot 01 was 61.25 tons/ha, become the lowest biomass plot

3.2.2.2 The K candel, S caseolaris, A corniculata, R stylosa community (Plot 02)

 Describe the structure:

This type of community is only found at Bai Nut - Con Lu To study the structure, status of this type, we installed a plot at coordinates N: 20012’58.9”, E: 106033’00.4”, plot size 20 x 20 m (400 m2)

This type of mangrove community is mixed by many species of mangroves Mangrove

communities in this plot are dominated by K candel, S caseolaris, A corniculata, R stylosa

participate but have not advantage

Stratification: Cross of canopy stage includes S caseolaris has height of 4-7 m The canopy stage includes 3 species of mangrove trees: K candel, R stylosa, S caseolaris has

height up to 2.5 - 3.2 m The lower part of the canopy stage consists two species of mangrove

trees: K candel and A corniculata has height of 1.5 - 2.0 m The shrubs and regenerated trees have some K candel, A corniculata, R stylosa

The number of K candel is more abundant than the rest in this plot In plot 02, the density of K candel decreased slightly because of the number of dead and broken trees in

typhoons The density decreased from 5,275 trees/ha to 4,825 tree/ha The other species have

no change in number and density, only some branches are broken In plot 02, K candel have the highest density, followed by A corniculata (1,150 trees/ha), S caseolaris (825 trees/ha),

R stylosa have the lowest density (400 trees/ha) Plot 02 had the lowest wood tree density,

the density recorded at the end of the study was 7,200 trees/ha

K candel, A corniculata, R stylosa have the same stem diameter S caseolaris have

different stem diameter

There are 3 species of mangrove can regenerated: K candel, A corniculata, R stylosa

A lot of K candel can regenerated, has height of 20 - 70 cm and the average density is about

16 to 19 plants/m2 Renewable K candel have good growth Regenerated A corniculata, R

stylosa regenerate with low density, poor quality

 Biomass

The average biomass recorded at the end of the study was 78.15 tons/ha, more than the

biomass of plot 01 at the same time S caseolaris has the highest average biomass and

increases slightly through the phase report (from 56.25 tons/ha - 57.25 tons /ha) Average

biomass of K candel in the second phase (10.225 tons /ha) decreased compared to the first

phase (10.45 tons/ha), the third phase showed signs of increase again (10.275 tons/ha) The

average biomass of A corniculata increased slightly through the phase report (1.85 - 2.075 tons/ha) Biomass of R stylosa in the second phase (9 tons/ha) decreased compared to the first phase (8.25 tons/ha) At the third stage, the biomass of R stylosa increased again (8.55

tons/ha)

3.2.2.3 The community of K candel, A corniculata participate (Plot 03)

 Describe the structure:

This type of community is located in the core zone of the national park, Con Lu area

To study this type of community, we installed a plot at coordinates N: 20013’74.9”, E:

106034’14.9”, the plot dimension was 20 x 20 m (400 m2)

This community is dominated by K candel, A corniculata participate but have not

advantage, the scrub stage is O ro plants This is a tree regeneration community so there is no similar age of trees

Stratification: The stratification in this OTC is not really clear The canopy stage

consists two species: K candel, A corniculata K candel has height up to 2-4 m A

corniculata has height from 1 to 2.5 m Shrubs, regenerated trees with the appearance of O ro

species has height from 0.5 to 0.7 m There are regenerated trees of two species K candel, A

corniculata

K candel community in this plot developed not really well Most trees are dry The

density of K candel decreased from 10,100 trees/ha (1st stage) to 9,650 trees/ha (3rd stage)

A corniculata community in plot 03 have good developement However, a small

number of dead A corniculata reduced the density of trees from 1,950 trees/ha (first stage) to

1,800 trees/ha (third stage) At the end of the study, the tree density in this plot was 11,275 trees/ha

K candel community in plot 03 has different stem diameter The growth in stem

diameter through the phase report is not very clear A corniculata in this plot have the similar

stem diameters, mainly in the range of 2.6 to 3.7 cm, stem diameter increased through the phase report

In this plot, two species of mangrove recorded low regeneration

 Biomass

K candel community in this plot have a slight decrease in density, the increase in stem

diameter is not clear, leading to a slight decrease in the biomass of the second phase (79.4 tons/ha) compared to the first phase (80.625 tons/ha) At the 3rd phase, when the number of

dead trees decreased sharply (only 7 trees), the biomass of K candel began to increase slightly (79.425 tons/ha) A corniculata community in plot 03 also had a slight decrease in density

but the stem diameter increased significantly, so the average biomass of this species had a slight increase through the phase report (from 7.8 tons/ha to 8.175 tons/ha) At the end of the study, the average biomass of wood mangroves in plot 03 was 3.504 tons/ha and the average biomass was 87.6 tons/ha

3.2.2.4 The community of A corniculata, K candel participate (Plot 04)

 Describe the structure:

This type of community is located in the core zone of Xuan Thuy National Park, Con Ngan area For this type of community study, we have established an plot at coordinates N:

20013’94.8”, E: 106034’21.2”, plot size 20 x 20 m (400 m2)

This is the type of mangrove community is dominated by A corniculata, K candel

participate but have not advantage, the scrub stage is O ro plants

Stratification: The canopy stage includes A corniculata, K candel with similar height

(3 to 4 m) The bushes, regenerated trees have the appearance of O ro plants with a height of

0.6 to 0.8 m Only K candel can regenerated with a height of 10 - 30 cm

Most of A corniculata plants in this plot are dry and deciduous, but there is no top of the tree crashed like plot 03, some A corniculata plants died The density of A corniculata decreased from 25,150 trees/ha (1st stage) to 24,525 trees/ha (3rd stage) The density of K

candel declined from 1,350 trees/ha (1st stage) to 1,250 trees/ha (3rd stage) At the end of the

study, plot 04 had a density of 25,775 trees/ha

A corniculata, K candel in plot 04 are not similar stem diameter A corniculata in

this plot has stem diameter about 2.6 – 3.5 cm The stem diameter has grown through the phase report

In this plot, only K candel can regenerated, the new tree grows normally

 Biomass

The biomass of both A corniculata and K candel increased slightly through the phase report The average biomass of A corniculata plants in the first stage was 95.95 tons/ha, the second was 98 tons/ha, the third was 100.5 tons/ha Biomass of K candel in the first phase

is 18.675 tons/ha, the second phase is 19.275 tons / ha, the third phase is 19.325 tons/ha At the end of the study, wood mangrove trees in plot 04 had an average biomass of 119.82 tons/ha

3.2.2.5 The A corniculata, S caseolaris, K candel community (Plot 05)

 Describe the structure:

This type of community is located in the core zone of national park, Con Ngan area (Bong Trang) For this type of community study, we established a plot at the coordinates N:20015’14.1”, E: 106034’13.8”, plot size 20 x 20 m (400 m2)

In this type of community, there are three species of mangrove: A corniculata, S

caseolaris, K candel The bush stage is O ro plants

Stratification: The cross of canopy stage is made up of S caseolaris species with a height of 4 - 6 m The canopy stage consists of A corniculata and K candel A corniculata has height of 1.3 - 2.7 m K candel has height of 1 - 3 m The bushes, regenerated trees have

the appearance of O ro plants with the height of 0.5 - 0.7 m The regenerated tree consists of

A corniculata and K candel with the height of 10 - 20 cm

In this type of community, A corniculata and K candel are grown and developed The young S caseolaris plants have dried and broken branches for a long time, currently there are only main branches and branches with a few shoots A corniculata in plot

well-04 have a very high density, the first phase recorded the density of plants is 61.325 trees/ha

and gradually reduced to the third stage to 59.400 trees/ha K candel density recorded in the

first and second stages was 3.875 trees/ha and reduced to 3.775 trees/ha in the third stage

because 4 trees damaged by the storm S caseolaris trees in OTC 05 have a stable density

during the phase with a density of 500 trees/ha Wood density in plot 05 at the end of the study was 63.675 trees/ha

K candel and S caseolaris are not similar stem diameter, but the growth of stem

diameter is clearly A corniculata in plot 05 had similar stem diameters and also increased

through the phase report

In plot 05, S caseolaris is non-regenerated species, only K candel and A corniculata

can regenerated with low speed

 Biomass

A corniculata have the high number of plants so the average biomass is highest The

average biomass of A corniculata in the second phase (157.975 tons/ha) was lower than the

first one (158.175 tons/ha) due to the decreasing of density In Phase 3, the stem diameter increase, the average biomass of this species (164.925 tons/ha) increased compared to the first