Ảnh hưởng của các dạng lập địa và chế độ triều lên khả năng tích lũy cacbon của rừng ngập mặn tại tỉnh cà mau (tt)

MINISTRY OF EDUCATION AND TRAINING
CANTHO UNIVERSITY

SUMMARY of THE PhD THESIS
Major: Soil and water environment
Code: 9440303

PhD student: Nguyen Ha Quoc Tin

Thesis title:

EFFECTS OF TOPOGRAPHY TYPES AND TIDE REGIMES ON THE
CARBON ACCUMULATION OF MANGROVES
IN CA MAU PROVINCE

Can Tho, 2018


THE RESEARCH PROJECT WAS DONE AT CANTHO UNIVERSITY

Scientific supervisors: Assoc. Prof. Dr. Le Tan Loi

The doctorate degree dissertation is to be defended in front of a Specialized Committee at the
state level

at Can Tho University

on …………………………………

Reviewer 1:

Reviewer 2:

The thesis can be referred at:
- School of Environment and Natural Resources, Can Tho University.
- Learning Resource Center of Can Tho University.
- National Library of Vietnam.

ii


LIST OF PUBLISHED WORKS

1. Nguyễn Hà Quốc Tín, Lê Tấn Lợi, Đỗ Thanh Tân Em, 2014. Research on
carbon accumulation of Rhizophora apiculata on the different mangrove types at Ngoc
Hien dictrict, Ca Mau province. Journal of Science and Technology, Viet Nam Academy
of Science and Technology 52 (3A): 274 – 279. ISSN: 0866 708X.
2. Nguyễn Hà Quốc Tín, Lê Tấn Lợi, 2015. Ảnh hưởng của cao trình đến khả năng tích
lũy cacbon trên mặt đất của rừng ngập mặn cồn Ông Trang, huyện Ngọc Hiển, tỉnh Cà
Mau. Tạp chí khoa học Trường Đại học Cần Thơ, số chuyên đề Môi trường và biến đổi
khí hậu: 218 – 225. ISSN: 1859-2333.
3. Nguyễn Hà Quốc Tín, Lê Tấn Lợi, Lý Hằng Ni, 2014. Nghiên cứu sự tích lũy
cacbon trong cây tại cồn Ông Trang, huyện Ngọc Hiển, tỉnh Cà Mau. Kỷ yếu Hội nghị
khoa học lần IX Trường Đại học Khoa học Tự nhiên, Đại học Quốc gia thành phố Hồ
Chí Minh: 18-25. ISBN: 978-604-82-1375-6.
4. Đỗ Thanh Tân Em, Nguyễn Hà Quốc Tín, Lê Tấn Lợi, 2014. Tích lũy cacbon của cây
Đước theo các dạng lập địa rừng tại huyện Ngọc Hiển tỉnh Cà Mau. Kỷ yếu Hội nghị
KHCN tuổi trẻ các trường đại học & cao đẳng khối Nông – Lâm – Ngư – Thủy toàn
quốc lần thứ VI năm 2014:853-856 (Bằng khen của Ban Chấp hành trung ương Đoàn
tặng cho báo cáo đạt giải nhì).

iii


CHAPTER 1: INTRODUCTION
1.1. Introduction
The main cause of global warming is the increase of the concentration of greenhouse
gases due to emissions of carbon dioxide (CO2). According to the IPCC, CO2 accounted for
60% of the causes of global warming, the CO2 concentration in the atmosphere had increased
by 28% from 288 ppm up 366 ppm in the 1850-1998 phase (IPCC, 2000). In the current
period, the concentration of CO2 increased of about 10% in 20-year cycles (UNFCCC, 2005).
Generally, in the context of the climate change, Vietnam is one of the countries located
in regions with a high risk. According to the predicted greenhouse gas emissions by the year
2030 in Vietnam, the greenhouse gas emissions of the manufacturing industry including
energy and agriculture were increasing rapidly, even for the energy sector in 2030 more than
14 times the fold in 1993 (396.35 million tons compared with 27.55 million tons). Only the
forestry sector were expected to gradually increase the amount of carbon absorption and up to
about 32.10 million tons in 2030 (Phan Minh Sang and Luu Canh Trung, 2005).
In general, forest and mangroves in particular play an important role in the
accumulation of carbon. Woods play an important role in reducing the impact of climate
change due to its influence to the global carbon cycle. The total amount of accumulated
carbon reserve of forests around the world, in the soil and the vegetation is about 830 Pg, in
which carbon in soil greater than 1.5 times the carbon stored in vegetation (Brown, 1997). For
tropical forests, up to 50% of the amount of carbon stored in vegetation and 50% of the
reserves in the soil (Dixon et al., 1994; Brown, 1997; IPCC, 2000; Pregitzer and Euskirchen,
2004). However, the deforestation in general and in particular mangrove forests in the world
as well as in Vietnam, and the Mekong delta especially in Ca Mau is going strong. In the year
2014, Ca Mau had an area of approximately 65,469 hectares of mangroves (Ministry of
agriculture and rural development, 2015). This issue has contributed to reduced CO2 emission
absorption by the degraded forests from which led to climate change.
The existence, distribution and development of mangrove trees depend on a number of

natural factors. According to Chapman (1977), the environmental factors had impact on the
formation and distribution of mangrove trees such as the temperature, the body, the tides, the
saltwater conditions. In addition, according to Robertson and Alongi (1992), the factors that
affected the distribution of mangrove forests including soil properties, the tide regimes,
terrain, useful minerals, loose of soil, wind, wave and flow activity. The distribution of
mangrove forests was mainly influenced by temperature (Duke et al., 2002) and humidity
(Saenger and Snedaker, 1993). According to Le Tan Loi (2010) the hydrologic regime had a
direct influence on growth and biomass of mangrove plant species. Previously, there were
many studies on the distribution, biomass and accumulation of carbon of the mangrove forest.
However, it had only identified the possibility of increasing biomass or carbon accumulation
of mangrove forests or just identifying the environmental factors of the mangrove forest in a
single way, but no mention of the influence of the natural environment elements work in
every relationship in which there are interacting to accumulate biomass as well as carbon,
particularly on the establishment of the different location.
1


From there, the thesis “Effects of topography types and tide regimes on the carbon
accumulation of mangroves in ca mau province” was done to study the growth and
development of mangrove forests based on the effects of the elements the environment
characterized in the form of established local and tidal regime to carbon accumulation
capacity of mangrove forest. The content of the thesis which was implemented in two areas,
Vam Lung and Ong Trang islets of Ngoc Hien district, Ca Mau province is the important
database for the management of mangrove forests and our nation to contribute for the
management of mangrove forests sustainable, multifunctional and minimize the impacts of
climate change.
1.2 Objectives
1.2.1 General Objective
To identify specific environmental factors on the topography types and the tidal regime
of the East Sea (Vam Lung estuarine) and the West Sea (Ong Trang estuarine) to find out the

influences as well as the relationships of the environmental factors to carbon accumulation
ability of mangroves in Ca Mau.
1.2.2 Specific objectives
- Identify environmental factors of the topography types in the East Sea (Vam Lung
estuarine) and the West Sea (Ong Trang estuarine).
- Determine the South Sea tidal regime (Vam Lung estuarine) and the West Sea (Ong
Trang estuarine).
- Determine the biomass and carbon accumulation capacity of mangroves in the
topography types in the East Sea (Vam Lung estuarine) and West Sea (Ong Trang estuarine).
- Assess the impacts of environmental factors and tidal regimes to carbon accumulation
capacity of mangroves in the East Sea (Vam Lung estuarine) and the West Sea (Ong Trang
estuarine).
1.3 The content of the study
- Survey of specific environmental factors of the topography types such as the
elevation of the ground, the frequency of flooding and depth of tidal, salinity of water in the
soil, pH, Eh, density and organic matter content.
- Survey and evaluation of biomass and carbon accumulation capacity of mangroves at
the the topography types.
- Determine the impacts of specific environmental factors of the topography types and
tidal regimes to carbon accumulation capacity of mangroves.
1.4 New findings of the thesis
The thesis provides data on specific environmental factors of topography types and tidal
regime affecting the ability to accumulate carbon of mangrove forests in Ca Mau, as the basis
for the management and development of forests mangrove and the amount of CO2 absorbed in
forest ecosystems in mitigating the impacts of natural disasters due to climate change.
2


1.5 Objects and scope of the research
1.5.1 Research objects

The objects of the study were water and soil in the East Sea and the West Sea, tidal
regime; mangrove plants in Vam Lung estuarine and Ong Trang islet to study topography
types on and tidal regimes affecting on the accumulation of carbon in mangrove forests in Ca
Mau province.
The objects of the study were the specific environmental factors of topography types
such as elevation, depth and frequency of inundation, soil pH, soil Eh, salinity of soil water, density,
and organic matter content in soil.
In addition, biomass and ability to accumulate carbon of mangroves in topography types
and the impacts of specific environmental factors of topography types and tidal regimes on
the accumulate carbon capacity of mangroves were the objects of research.
1.5.2 Scope of the research
The research was implemented in the mangroves at Ca Mau Province from January
2014 to December 2014.
1.6 The scientific and practical significance of the thesis
1.6.1 Scientific significance
The research results have scientific meanings and application in the conservation,
management and rational use of resources, mangroves in sustainable ways to contribute to
mitigating the impact of natural disasters due to climate change. Additionally, the thesis also
provides references in the study of mangrove forests in Ca Mau in particular and Vietnam in
general, especially the issues of further study of the relationship between the elements of the
natural environment and carbon accumulation capacity of mangrove ecosystem
1.6.2 Practical significance
Thesis provides scientific information about:
- The specific environmental factors of the topography types and tidal regimes.
- The capacity for carbon accumulation of the mangroves.
- The impacst of specific environmental factors of the topography types and tidal
regimes to carbon accumulation capacity of mangrove forests in Ca Mau.

3

CHAPTER 2: LITERATURE REVIEWS
2.1. The concept of Mangroves
According to FAO (1994), mangroves are structured vegetation typical of coastal
areas of tropical and subtropical, is one of the forest ecosystems important submerged. They
are also known as coastal forests, tidal forests or mangroves. Generally, mangroves include
trees and shrubs growing under high water level of the tide. Their root systems often flooded
salt, or may be diluted by freshwater runoff surface and flooded only once or twice a year.
"Mangroves" in English is a term that is difficult to define precisely. According to
some authors, the word "mangrove" is used to indicate the species or a forest with many
species living in the environment of coastal wetlands. Communities, mangroves include more
detailed and they plant a majority of no kinship, but there are common traits of character
adapted morphology, physiology and reproduction suitable for living environment extremely
difficult towels are submerged, lacking air and soil instability. Based on the distribution of
mangrove species are heading tropical and subtropical species, although there are some
species in the deep of the South or North of the nearby temperate area (Nguyen Hoang Tri,
1999).
Mangrove are the trees growing on the transition zone between land and sea in tropical
and subtropical, where trees exist in conditions of high salinity, tidal, wind, temperature high,
silt and anaerobic. Mangroves include trees, shrubs and herbaceous plants that belong to many
different plant species but the common characteristics are evergreen, physiological
characteristics similar and adapted for living conditions influenced by regime tide and
anaerobic (Vien Ngoc Nam, 2010). According to Clough (2013), the mangrove forest is a
complex diversity of trees, shrubs and where ferns grow in the habitat characteristics - terrain
tide between land and sea, along the coast of the tropical and subtropical worldwide.
Mangroves are also often used to describe the composition of plant communities and their
habitats. Along with the fauna and other organisms in the same environment, they form a
typical ecosystem types, such as mangrove ecosystems.
2.2 The topography and topography typyes of mangrove
2.2.1 Concept of topography

- The topography is the habitat of a species or set of species under the influence of all
external factors impact on them (Ministry of Agriculture Industry and rural Development,
1996).
- According to Hoang Van Than and Nguyen Van Them (2000), the topography is
inhabited by organisms, or a set of ecological factors, determine the existence of the biome.
- The topography is a certain territory with all of the external factors affecting the
growth of plants. Tpography in the narrow sense consists of 3 components: climate,
topography, soil, and in a broad sense includes four components: climate, topography, soil
and plant and animal world. The basic unit in the classification of topography is topography
types and group of topography types, including: (1) Type of topography is a collection of
separate topography including elements for constituting types of topography considered
4


uniformity, is the basic unit, the final classification system to evaluate the topography. (2)
Group types of topography is a collection of types of topography have the general soil fertility
and similar use and close relationships in terms of ecology and the same business methods
(Ngo Dinh Que, 2011; Ngo Dinh Que, 2011; Ngo Dinh Que and Nguyen Xuan Quat, 2012;
Do Dinh Sam and collaborators, 2005a; Forest Inventory and Planning Institute, 2000).
2.2.2 Classification mangrove terrain
According Lugo (1974) divided mangrove topography into the following types:
+ Topography of coastal mangroves (Fring Mangroves) is formed in seaside or island
with morphology higher than the average high of tide with well-developed root system and
sometimes influenced by wind and storm.
+ Topography of riverine mangrove (Riverine Mangroves) is formed in the forests
along the rivers or creeks with low morphology and tide daily.
+ Topography of mangrove in island or islet is the morphology with mangroves on the
island or islet in shallow bays or estuaries with the flooding morphology at high tide the plant
relatively homogeneous terrain.
+ Topography of mangrove basin is topography with the mangrove formed at the

seaside, river ine and islet.
+ Topography of difficult mangrove forests is mangrove formed at the low site of
coastline with few species and developing in conditions of malnutrition.
According to Ngo Dinh Que and Ngo An (2001), based on the results of the survey of
topography about the distribution of vegetation, soil and plants in coastal areas of the Mekong
Delta, we can propose important factors relating to the growth of crops. 3 main factors which
were selected. They were: Soil type: coastal mangrove area is divided into 2 categories”. They
are mangrove Soil and Mangrove Soil with potential Aluminum Sulfate,
Regimes of flooding tides
- The maturation of the soil is important bases to the distribution of vegetation,
condition and growth capacity of the plant, can be divided into 4 levels: slush, mud tight,
lightning soft, hard clay.
According to Do Dinh Sam et al. (2005) evaluating the production potential for
mangrove land Mekong Delta region is based on the criteria of soils, soil maturity, organic
matter content and tidal regime. According to Doan Dinh Tam (2011), there are many factors
affecting the survival, growth and development of mangroves as topography, precipitation
patterns, temperature, salinity, tidal regime, maturity of the soil ... However, after considering
the role of each element, choose 4 main factors that tidal regime, soil type, mechanical
composition and maturity of the soil to divide up local establishments. In summary, based on
research on the definition and division of the site mangrove forests of the authors and abroad,
the author has conducted select divide the site mangrove tidal regime, physical conditions,
land and chemical plants.

5


2.3 Factors affecting the distribution of mangroves
Existence and distribution of mangrove trees depend on a number of basic
elements. According to Chapman (1977), the environmental factors affecting the formation
and distribution of mangrove trees such as temperature, substratum, tide, saltwater

conditions. However, according to Robertson and Alongi (1992), the factors affecting the
distribution of mangrove forests include land, tidal, topography, mineral useful, workability of
the soil, the wind, the operation of currents and waves. The distribution of mangroves is
influenced primarily by temperature (Duke et al., 2002) and humidity (and Snedaker Saenger,
1993). Phan Nguyen Hong and Hoang Thi San (1993) said that the factors affecting the
distribution of mangroves in Ca Mau is the climate factors, hydrology factors, soil and
topography. According to Tran Phu Cuong (1996) factors affecting the formation of
mangrove belt under trees as salinity and soil characteristics.
Frequency and duration of the flooding tide is an important factor to determine the
distribution of sites and species composition of mangroves (Wilkinson and Baker, 1997).Tide
is an important factor for the distribution and growth of mangroves, because not only has a
direct impact on the plant due to the level and duration of flooding, but also affects many
other factors such as the structure, soil salinity (Phan Nguyen Hong, 1999).
Frequency and duration of flooding tide are the important factors to determine the site,
distribution and composition of species of mangroves. Some authors have divided the
mangroves into three levels related to the distribution of mangrove vegetation is low intertidal
zone, medium and high (Wilkie and Fortuna, 2003). According to Le Tan Loi (2008),
frequency and tidal influence primary productivity and the distribution of species, and also
affects other factors such as the deposition of silt, the accumulation of organic matter body
Watson (1928) has classified the distribution of mangrove plants in the group:
+ Group 1: The high intertidal zone. In this area often appears only type used
(Rhizophora mucronata); Group 2: The average high tide flooded. Often find species like
Avicennia alba, Avicennia marina and Sonneretia alba and Rhizophora mucronata formed
along the tributaries.; Group 3: The normal tidal. Mangroves thrive in this group, especially
Rhizophora, ceriops Tagal, Xylocarpus, and Excoecaria; Group 4: The submerged by the
tide. This region is too dry for Rhizophora but unstable for Parrots Bruguiera, Xylocarpus and
Price Excoecaria; Group 5: The areas with unusual tidal regime. Most plants in the region
have Bruguiera gymnorhira, Intsia bijuca, Heritiera littoralis, Excoecaria agallocha and Nypa
frutican.
Figure 2.1: Levels of tide flooded divided by Waston (1928)

Levels

The characteristics of flooding tide

Flooding hits/month

1

High tide flooded land

50-62

2

The average high tide flooded land

45-56

3

By wetland tide Middle normal high

20-45

4

The land is only flooded when the tide

2-20

5

The land is only flooded when the tide anomaly
6

2


De Haan (1931) divided tidal levels into 5 groups, but by the number of days in month
and flooded about lower oscillating way division of Watson. De Haan's group division is as
follows: Group 1: The high flooding tide, flooding with 20-day average for the month; Group
2: The average high flooding tide, with an average of 10-19 days submerged in months;
Group 3: As usual intertidal areas, with an average of 4-9 days submerged in months; Group
4: The water submerged by the tide, with an average of 2-4 days in the month flooded; Group
5: The areas with unusual tidal regime, with an average of 2 days intertidal month. Currently
in Vietnam, tide was classified in eighth tropical tide along the coast, can be grouped into 4
zones are named as follows: the central coast, the coast north east coast of the South and the
West Coast of Ca Mau. Central coast mode irregular tide. North coast mode are diurnal while
the southeast coast there are semi-diurnal. West coast of Ca Mau has both diurnal tide and the
tide though diurnal tide prevails.
2.4. carbon accumulation of mangroves
The local and foreign scientists researched the ability of carbon deposition in different
kinds of forests, many trees. Carbon (carbon content rate is calculated by %) and a portion of
the dry biomass (defined trees, branches, leaves, roots......). Carbon storage, quality is a tank
of carbon. The tank is carbon storage tank. For the forest, there are 5 kinds of carbon: carbon
tank (living in wood biomass above and below ground); carbon in wood tree (the dead trees
and in stream layer); carbon storage in carpet fresh, shrub (regenerated tree, shrub, grass);
carbon storage in the project (block of wood, carpet falling objects, humus) and organic
carbon (plume local and RCFEE tons, 2012).
Vien Ngoc Nam et al. (1996) researched biomass and primary productivity mangrove

(Rhizophora apiculata) grew in Can Gio. The author used the standard method for data
collection method and vibration - based on Ong Jin and collaborators (1983), the biomass of
mangrove at the age of 4, 8, 12, 16 and 21 recorded sequentially 16,24 dried tons / ha, 89,01
dried tons / ha 118,21 dried tons / ha, ha, ha, 138,98 dried tons / dry 139,98 dried tons / ha.
This research has focused on the definition of part of the ground biomass of mangrove.
Komiyama et al .(2000) implemented the study "The proportion of biomass on the ground and
the roots of mangroves secondary Cetiops Tagal (PERR.) CB Robinson", has counted the
biomass above ground and below-ground root size. Results obtained ratio above ground
biomass and the root of limestone (ceriops Tagal) in southern Thailand is 1.05, relative
biomass was 53.35 tons / ha, spike: 23.61 tons / ha; Leaf: 13.29 tons / ha; Root: 1.99 tons/ ha
and ground is 87.51 tons/ha
Donato et al. (2009) gave a number of specific methods to calculate the carbon in the
fuel tank of the mangrove in Bangladesh. These included soil carbon pool, plant biomass, on
the ground of the tree, the tree sprouted, you young, new life, new seedling germination and
young, dead trees, dead tree wood, forest animal fell on the floor. The total carbon reserved of
the total forest carbon pool and in all.
In short, most of the research focused on evaluating and determining the quantity of
carbon stored in a tank, including body parts, carbon accumulation in the biomass of branches
and leaves, roots in the ground or through the accumulation of biomass of fallen depend on
the land in the forest carbon on the floor or the depth. Especially some research attention to
7


calculate the ground biomass of the root, but the limited scope of application is expensive,
need time. However, the study by Donato (2009) showed the full results of the accumulation
of carbon mangroves. On the other hand, these studies stopped at determining the ability to
accumulate carbon, but no studies related to the natural conditions affect the ability to
accumulate carbon of forests in general and mangroves in particular.

8

CHAPTER 3: METHODS AND MEANS OF RESEARCH
3.1 Research methods
3.1.1 Methods of collecting secondary data
The subject has inherited a number of documents related to the emerging field of
research on mangroves which were collected at Nam Can hydro-meteorological stations as
tidal data 2014
- Map of mangroves at the site of Vam Lung estuarine and Ong Trang islet
- The scientific reports from conferences, seminars and resources from the Schools
and Institutes, other research centers.
3.2.1 Laboratory layout method
The research was conducted in two areas of mangrove in Vam Lung and ong Trang
estuarine in Ngoc Hien district, Ca Mau province.
At Vam Lung estuarine in Tan An village, Ngoc Hien district, the author based on the
morphology altitude, the flooding tide and vegetation to divide into 3 coastal topography,
estuarine and riverine. On each place, setting created a cut 150 m in length and perpendicular
to the shoreline, on each cut layout 6 standard cell form a circle and have an area of 153.86
m2. A total of 18 standard plots were collected samples and measurements in the area of the
river Vam Lung.
At the Ong Trang estuarine, the studies were arranged in Ong Trang islet (inside islet) in
Vien An village, Ngoc Hien district. Based on the altitude of the topography, the flooding tide
and conducted vegetation divided into 3 types of site as in front of islet, the central of islet and
the end of islet. At each place setting, create a 150 m long and square cut slices with each
coast cut the layout standard form plots 6 circular and has an area of 153.86 m 2. Similarly,
there were a total of 18 standard plots at Ong Trang islet to measure and collect data.
In each plot, standard measurements of environmental parameters (pH, Eh, the salinity
of the water in the soil, density, organic matter content), measure the biomass of trees were
collected samples to shed (shoots, leaves, stems, etc.). The process of sampling was done
according to the sampling process is to assess the carbon reserve in the wetland ecosystems of

the Tropical Forestry Research Center International (CIFOR) (Kauffman, & Donato., 2012).
Layout experiments and collecting samples as Figure 3.1, 3.2 and 3.3.

9


Fig 3.1: Layout of experiments in Vam Lung and Ong Trang islet

Figure 3.2: Diagram of the layout of the standard plot

10


Figure 3.3: Layout of sampling in a standard plot
3.1.3 Data collection
The process of collection of biomass plants, specimens fall, soil sample samples to
measure Ph soil, Ooidative voltage reduction (Eh), the salinity of water in the soil, organic
content in the soil, determining the amount of carbon accumulation in soils were done
according to the sampling process is to assess the carbon reserve in the wetland ecosystems of
the Tropical Forestry Research Center International (CIFOR) (Kauffman, & Donato., 2012).
Flooding tide measurement was done according to English et al. (1997).

11


3.2 Schematic layout of experiment layout

Figure 3.8 Schematic diagram of experiment layout

12

CHAPTER 4: RESULTS AND DISCUSSIONS
4.1 Environmental factors of soil, water and carbon accumulation in Vam Lung
4.1.1 Land and water environment

Ground elevation (cm)

The research results at Vam Lung showed that the riverine had the lowest elevation,
followed by the estuarine and the highest is the fringe so the riverine had the number of
inundation/year and the highest depth of inundation, followed by estuarine and the lowest is
the fringe. Salinity values of soil water, pH and soil Eh were highest in fringe, followed by
estuarine and lowest at riverine. The highest soil density in the fringe, followed by the riverine
and lowest at the estuarine. Organic matter in the highest soil at the estuarine, followed by the
riverine and the lowest at the fringe.
Fringe

300

Estuarine

Riverine

250
200
150
100
50
0
T1

T2

T3

T4

T5

T6

frequency of inundation
(day/year)

Center of standard plots
400

Fringe

Estuarine

Riverine

350
300
250
200
150
100
50

0
T1

T2

T3

T4

T5

T6

Center of standard plots
Depth of inundation
(cm)

100
Fringe

Estuarine

Riverine

80
60
40

20
0

T1

T2

T3
T4
T5
Center of standard plots

T6

Figure 4.1: Elevation, inundation frequency and tidal depth of
mangrove forest in Vam Lung
13


4.1.2 Carbon accumulation in Vam Lung Mangrove Forest
Carbon sequestration on standing trees was the lowest in the fringe topography,
followed by the estuarine topography and the highest at riverine topography. C accumulation
in litter fall was low in the riverine topography, followed by the estuarine and the highest in
the fringe topography and they were not statistically diferent. C accumulation in soil was the
highest in the fringe topography, followed by the riverine and the highest at estuarine
topography and they were not statistically different. The higest roots C accumulation was
different in the fringe topography which was the the lowest roots C accumulation and they
both they were not statistically diferent with higest roots C accumulation in estuarine
topography. The results showed that total C accumulation was not statistically different, the
highest trend was in riverine, followed by estuarine and lowest in fringe.
4.1.3 Impacts of soil, water environment on carbon accumulation
4.1.3.1 Impact of inundation frequency on carbon accumulation
At the fringe topography, inundation frequency related with carbon accumulation of

standing trees, litter fall, roots and soil in which inundation frequency only correlated with
carbon accumulation in soil with coefficient r = 0.50 and carbon in litter fall with fallow
coefficient r = 0.73.
At estuarine, inundation frequency related with carbon accumulation of standing trees,
downed deadwood, roots and soil, but inundation frequency only correlated with carbon
accumulation with a coefficient of r = 0.72.
4.1.3.2 Effect of depth of inundation on carbon accumulation
Analytical results showed that there was a relationship between the depth of inundation
and carbon accumulation of standing trees, downed deadwood, roots and soil in mangrove
forest at the topography types in Vam Lung. At the fringe topography, the depth of inundation
only correlated with carbon accumulaticon in soil with coefficient r = 0.59 and carbon in
downed deadwood with coefficient r = 0.77. At the estuarine topography, inundation depth
was only correlated with carbon accumulation in downed deadwood with a coefficient of r =
0.66. At the riverine, the the depth of inundation only correlated with the accumulation of
standing trees with coefficient r = 0.54, carbon in downed deadwood with coefficient r = 0.65
and carbon roots with coefficient r = 0.55.
4.1.4.3 Impact of physical and chemical factors and carbon accumulation
- Impacts of physical, chemical and carbon accumulation in soil: At the fringe
topography, carbon accumulation in the soil was affected by the physical and chemical factors
was the soil pH with coefficient r = 0.72; Eh of soil with coefficient r = 0.76; soil density with
coefficient r = 0.96 and organic matter with coefficient r = 0.59. At the estuarine topography,
carbon accumulation in soil affected by soil physical and chemical factors was pH of soil with
coefficient r = 0.59 and soil density of coefficient r = 0.95. At the riverine topography, carbon
accumulation in soil affected by soil physical and chemical factors was the salinity of water in
soil with coefficient r = 0.50. This was in line with the research results of Dang Trung Tan
14


(2007) at Ca Mau mangrove forest that in the mangrove forest environment, the higher the
soil density, the higher the carbon accumulation and vice versa.

- Impacts of physical and chemical factors and carbon accumulation of standing trees:
At the fringe topography, carbon accumulation of stading trees was affected by the physical
and chemical factors was the soil pH coefficient r = 0.80; soil Eh with coefficient r = 0.69 and
soil density with coefficient r = 0.76. In the estuarine topography, carbon accumulation of
standing strees was affected by the physical and chemical factors was the density of r = 0.60
and organic matter coefficient r = 0.56. At the riverine topography, accumulation of C
standing trees was affected by the physical and chemical factors was the salinity of water in
soil with the coefficient of r = 0.53 and Eh soil with coefficient r = 0.52.
- Impacts of physical, chemical and carbon accumulation of down death wood: At the
fringe topography, carbon accumulation in downed deadwood was related to soil physical and
chemical factors but was mainly affected by soil pH with coefficient r = 0.84; Eh of soil with
coefficient r = 0.89 and soil density with coefficient r = 0.52. At estuarine topography,
accumulation of carbon in downed deadwood was related to the physical and chemical factors
but was mainly affected by soil pH with the coefficient of r = 0.60; salinity of soil water with
coefficient r = 0.87 and soil Eh with coefficient r = 0.97. At the riverine topography, carbon
accumulation in downed deadwood was related to physical and chemical factors but was
mainly affected by soil organic matter with coefficient r = 0.74.
- Impacts of physical, chemical and roots carbon accumulation of standing trees: At the
fringe topography, carbon accumulation was related to soil physical and chemical factors but
was mainly affected by soil pH with coefficient r = 0.80; Eh soil with coefficient r = 0.67 and
soil density with coefficient r = 0.75. At estuarine topography, accumulation of carbon was
related to the physical and chemical factors but was mainly affected by soil density with the
coefficient of r = 0.57 and organic matter with coefficient r = 0.52. At the riverine
topography, carbon accumulation was related to physical and chemical factors but was mainly
affected by soil Eh with the coefficient of r = 0.50; salinity of soil water with coefficient r =
0.52.
4.1.4 The relationship between the environment and the carbon accumulation
4.1.4.1 Correlation between soil environmental parameters
accumulation

and soil carbon

Based on the results of Table 4.1, the multivariable regression equation is predicted
based on variables such as soil weight and organic matter in soil. So the equation used to
predict is: Carbon in soil = -123.73 + 0.83*soil density + 0.49*organic matter in soil (1)
Equation (1) showed that the correlation between environmental parameters and carbon
accumulation is different. In particular, soil pH or organic matter content in soil were
parameters of the environment which are strongly correlated with the accumulation of carbon
in the soil. This was in line with the research findings of Hong and San (1993) in Ca Mau that
the higher the soil density, the higher the carbon accumulation in the soil. Similarly, organic
matter in soil was also an environmental factor that greatly influenced the accumulation of
carbon in the soil.
15


Table 4.1: Interdependence between soil parameters and carbon accumulation in soil
Environmental parameter
Constant
pH
Salinity
Eh
Density
organic matter

Constants B
21,31

Beta coefficient
-0,11
-0,26

0,46
-0,21
-0,37

Significant level
0,07
0,69
0,33
0,19
0,57
0,24

*: Show statistically significant level at 5% level, **: Show statistically significant level
at significance level of 1%
4.1.4.2 Correlation between soil parameters and carbon accumulation of tree roots
Results of the correlation between soil environment parameters and roots carbon
accumulation were presented in Table 4.2. Based on the results of Table 4.2, there was no
correlation between land environment parameter variables and carbon accumulation of tree
roots.
Table 4.2: Interrelations between soil environmental parameters and roots carbon
Environmental
Constants B
Beta coefficient
Significant level
parameter
Constant
21,31
0,07
pH
-0,11

0,69
Salinity
-0,26
0,33
Eh
0,46
0,19
Density
-0,21
0,57
organic matter
-0,37
0,24

*: Show statistically significant level at 5% level, **: Show statistically significant level
at significance level of 1%
4.1.4.3 Correlation between soil environmental parameters and carbon of standing trees
Results of the correlation between soil environmental parameters and carbon
accumulation of standing trees were presented in Table 4.3. Based on the results of Table 4.3,
there was not correlation between land environment parameter variables and carbon
accumulation of standing trees.
Table 4.3: Interrelations between soil parameters and standing trees carbon
Environmental
Constants B Beta coefficient
Significant level
parameter
Constant
13.96
0.12
pH

-0.18
0.35
Salinity
-0.12
0.54
Eh
0.34
0.15
Density
-0.01
0.98
organic matter
-0.02
0.91
*: Show statistically significant level at 5% level, **: Show statistically significant level
at significance level of 1%

16


4.1.4.4 Correlation between soil environmental parameters and carbon accumulation in
downed deadwood
The results of the analysis of the correlation between soil environmental parameters
and the accumulation of carbon in downed deadwood were presented in Table 4.4. The results
showed that there is no relationship between the environmental parameter variables and
carbon accumulation in downed deadwood.
Table 4.4: The correlation between soil parameters and carbon in downed
deadwood
Environmental
Constants B Beta coefficient

Significant level
parameter
Constant
13.96
0.12
pH
-0.18
0.35
Salinity
-0.12
0.54
Eh
0.34
0.15
Density
-0.01
0.98
organic matter
-0.02
0.91
*: Show statistically significant level at 5% level, **: Show statistically significant
level at significance level of 1%
The results of Table 4.4 showed that it was not predicted the equation showing the
correlation between soil environment parameters and the accumulation of carbon in downed
deadwood. The explanation was that downed deadwood not influenced of the soil
environmental factors but it would be greatly affected by seasons or tidal regimes. This result
was also consistent with the study by Nguyen Hoang Tri (1999) and Dang Trung Tan (2007)
in Ca Mau that the downed deadwood was influenced by the tide regime.
4.2 Soil, water environment and carbon accumulation in Ong Trang islet mangrove
forest

4.2.1 Soil and water environment
The results research at Ong Trang islet showed that the tip of Ong Trang islet
topography had the lowest elevation, followed by the middle of Ong Trang islet topography
and the highest was the top of Ong Trang islet topography so the tip of Ong Trang islet
topography had the highest number of inundation/year and the depth unindation, followed by
middle of Ong Trang islet topography and the lowest was the top of Ong Trang islet
topography. The pH value was the highest at the middle of Ong Trang islet topography,
followed by the tip of Ong Trang islet and the lowest at the top of Ong Trang islet
topography. The Eh, salinity of soil water, and organic matter in soil value were not different
at three sites in Ong Trang islet. The soil density was the highest in the top of Ong Trang islet
topography, followed by the middle of Ong Trang islet and lowest at the tip of Ong Trang
islet topography.

17


Ground elevation (cm)

120

Top of islet

Middle of islet

Tip of islet

T3

T5

100
80
60
40
20
0

T1

T2

T4

T6

Center of standard plots
600

Top of islet

Middle of islet

Tip of islet

frequency of inundation
(day/year)

500
400
300

200
100
0

T1

T2

Top of islet

T3
T4
Center of standard plots
Middle of islet

T5

T6

Tip of islet

Depth of inundation (cm)

30
25
20

15
10
5

0
T1

T2

T3

T4

T5

T6

Center of standard plots

Figure 4.2: Elevation, inundation frequency and tidal depth of
mangrove forest in Ong Trang

18


4.2.2 Carbon accumulation in Ong Trang islet Mangrove Forest
The accumulation in soil was the highest and statistically diferent in the top of Ong
Trang islet topography, followed by the middle of Ong Trang islet and lowest at the tip of
Ong Trang islet topography. C accumulation in litter fall, standing and root trees was not
different in three topographies at Ong Trang islet. Total C accumulation in 03 types of
mangrove forest at Ong Trang islet was composed of C accumulation of standing trees,
standing roots, downed deadwood and in soil. The results showed that the total C
accumulation was not statistically different, the highest at the tip of Ong Trang islet
topography, followed by the top of Ong Trang islet and lowest at the middle of Ong Trang

islet topography.
4.2.3. Impact of soil and water environment conditions on carbon accumulation in
mangrove at Ong Trang islet
4.2.3.1 Impact of inundation frequency on carbon accumulation
At the top, middle and tip of the islet, the inundation frequency related with carbon
accumulation of standing trees, downed deadwood, roots and soil in which the inundation
frequency only correlated with carbon accumulation in downed deadwood with a coefficient
of r = 0.92 (at the top); r = 0,42 (at the middle) and r = 0.92 (at the tip).
4.2.3.2 Effect of inundation depth of tide on carbon accumulation
At the topography of the top and middle of islet, the inundation depth of tide related
with the accumulation of standing trees, downed deadwood, roots and soil in which the
inundation depth of tide only correlated with carbon accumulation in downed deadwood with
a coefficient of r = 0.93 (at the top) and r = 0.33 (at the middle).
At the tip of the islet, the inundation depth related with the accumulation of standing
trees, downed deadwood, roots and soil in which the inundation depth only correlated with
carbon accumulation in soil with coefficient r = 0.60.
4.2.3.3 Impacts of physical and chemical factors and carbon accumulation
- The impact of physical and chemical factors on carbon accumulation in soil
At the top of the islet, the physical and chemical factors had a relationship and affect the
accumulation of C soil except the salinity of water in the soil. In the middle of the islet, soil
physical and chemical factors are associated with carbon accumulation in soil but only soil pH
and Eh correlated with soil carbon accumulation. At the tip of the islet, the soil physical and
chemical factors were related to carbon accumulation in the soil in which only the soil pH and
density were correlated with the carbon accumulation in the soil.
The analysis of the relationship between soil physical and chemical factors and soil
carbon accumulation in all three sites at Ong Trang islet showed a positive correlation
between salinity parameters, Eh, organic matter content and carbon accumulation in soil. For
salinity parameters there was a direct correlation with carbon accumulation in soil with a
correlation coefficient r = 0.56. In addition, Eh was also positively correlated with carbon
accumulation in the soil with coefficient r = 0.70. The correlation analysis also showed that

organic matter content in soil was also correlated with carbon accumulation in soil with
19


coefficient r = 0.42. Soil density was correlated with carbon accumulation in soil with
coefficient of correlation r = 0.87. This was in line with the research results of Dang Trung
Tan (2007) at Ca Mau mangrove forest that in the mangrove soil, the higher the organic
matter content in the soil, the higher the carbon accumulation capacity and vice versa.
- Impacts of physical and chemical factors on accumulation of carbon in standing trees
At the top of the islet, the physical and chemical factors were related to carbon
accumulation of standing trees, but only organic matter and Eh were correlated with carbon
accumulation of standing trees. In the middle of the islet, the soil physical and chemical
factors were related but not correlated with accumulation of standing trees. At the tip of the
islet, the soil physical and chemical factors were related to carbon accumulation in the soil in
which only the soil pH and density were correlated with the carbon accumulation in the soil.
The analysis of the relationship between soil chemistry and carbon accumulation of
standing trees showed a negative relationship between soil salinity parameters, soil Eh and
carbon accumulation of standing trees. In particular, salinity of the soil had a relatively
negative correlation with the carbon accumulation in standing trees with coefficient r = 0.32.
This was in line with the research results of Nguyen Hoang Tri (1999) that in the mangrove
forest, if the salinity of the soil was high, it was related to the growth of mangrove trees
leading to affect on biomass accumulation and carbon of mangroves. In addition, soil Eh was
also negatively correlated with carbon accumulation in standing trees with coefficients r =
0.36. This suggests that if the soil environment has high Eh, it would affect the growth of
mangrove trees, which reduced the carbon accumulation capacity in the tree.
- The impact of soil physical and chemical factors on carbon accumulation in downed
deadwood
At the top of the islet, the physical and chemical factors were related with carbon
accumulation in downed deadwood but only salinity and Eh correlated with carbon
accumulation in downed deadwood. In the middle and at the end of the islet, the physical and

chemical factors were related but not correlated with accumulation in downed deadwood.
- Impacts of physical and chemical factors on roots carbon accumulation of standing
trees
Based on the analysis of the relationship between soil chemistry and roots carbon
accumulation of standing trees showed that soil physical and chemical factors were correlated
with roots carbon accumulation of standing trees but had no correlation.
4.2.4 Relationship between soil environmental parameters and carbon accumulation
4.2.4.1 Correlation between soil parameter and soil carbon accumulation
The results of the analysis of the correlation between soil environmental parameters
and the accumulation of carbon in soil were presented in Table 4.5. The results of Table 4.5
showed that there was a correlation between environmental parameters and carbon
accumulation.

20


Table 4.5: The interrelation between soil environmental parameters and soil carbon accumulation
Environmental
Constants B
Beta coefficient
Significant level
parameter
Constant
-169,75
0,23
pH
0,01
0,96
Salinity
-0,44

0,75
Eh
0,12
0,44
Density
0,79
0,00**
organic matter
0,26
0,03*

*: Show statistically significant level at 5% level, **: Show statistically significant
level at significance level of 1%
Based on the results of Table 4.5, multivariable regression is predicted based on
variables including density and organic matter in soil. So the equation used to predict is:
Carbon in soil = -169.75 + 0.79 * soil density + 0.26 * organic matter in soil (1)
Equation (1) showed that the correlation between environmental parameters and
carbon accumulation is different. In particular, density and organic matter content in soil were
positively correlated with the accumulation of carbon in the soil. This was in line with the
research findings of Hong and San (1993) in Ca Mau that the higher the soil density, the
higher the carbon accumulation in the soil. Similarly, organic matter in soil was also an
environmental factor that greatly influenced the accumulation of carbon in the soil.
4.2.4.2. Correlation between soil parameters and roots carbon accumulation
Results of the correlation between soil parameters and root carbon accumulation were
presented in Table 4.6. Based on the results of Table 4.6, there was no correlation between the
soil environmental parameter variables and the root carbon accumulation.
Table 4.6: Interrelations between soil environmental parameters and root carbon accumulation.
Environmental
Constants B
Beta coefficient

Significant level
parameter
Constant
59,49
0,79
pH
0,19
0,46
Salinity
-0,37
0,24
Eh
-0,34
0,90
Density
0,16
0,63
organic matter
-0,23
0,37

*: Show statistically significant level at 5% level, **: Show statistically significant
level at significance level of 1%
Based on the results of Table 4.6, it was not possible to develop an equation showing
the correlation between soil environmental parameters and carbon accumulation in tree roots.
4.2.4.3 Correlation between soil environmental parameters and carbon accumulation of
standing trees
Results of the correlation between soil environmental parameters and carbon
accumulation of standing trees were presented in Table 4.7. Based on the results of Table 4.7,
there was no correlation between the environmental parameter variables and the carbon

accumulation of standing trees.
21


Table 4.7: Interrelations between soil parameters and carbon of standing trees
Environmental
Constants B Beta coefficient
Significant level
parameter
Constant
244,06
0,69
pH
0,17
0,48
Salinity
-0,42
0,18
Eh
-0,06
0,86
Density
0,12
0,72
organic matter
-0,18
0,48
*: Show statistically significant level at 5% level, **: Show statistically significant
level at significance level of 1%
Similarly, the results of Table 4.7 showed that no equation for the relationship

between soil environment parameters and carbon accumulation in standing trees was
constructed.
4.2.4.4 Correlation between soil environmental factors and carbon accumulation in
downed deadwood
Results of the correlation between soil environmental parameters and carbon
accumulation in downed deadwood were presented in Table 4.8. Based on the results of Table
4.8, there was no correlation between the environmental parameter variables and the carbon
accumulation in downed deadwood.
Table 4.8: The correlation between soil parameters and carbon in downed deadwood
Environmental parameter
Constants B
Beta coefficient
Significant level
Constant
12,27
0,39
pH
-0,11
0,69
Salinity
-0,14
0,68
Eh
0,33
0,41
Density
0,01
0,99
organic matter
0,06

0,82
*: Show statistically significant level at 5% level, **: Show statistically significant level at significance
level of 1%

Based on the results of Table 4.8, it was not possible to predict the equation showing
the relationship between soil environmental parameters and the accumulation of carbon in
downed deadwood. The explanation was that downed deadwood will be greatly affected by
environmental conditions such as seasons or tidal regimes. This result was also consistent
with the study by Nguyen Hoang Tri (1999) and Dang Trung Tan (2007) in Ca Mau that the
downed deadwood was influenced by the tide regime.

22