MINISTRY OF EDUCATION AND TRAINING
CAN THO UNIVERSITY
PhD THESIS SUMMARY
Soil and water environment
Code: 62 44 03 03
VO NGUON THAO
RESEARCH ON THE STRUCTURE CHARACTERISTICS AND
NUTRIENT OF MANGROVE AT ONG TRANG MANGROVE
ISLET, CA MAU PROVINE
Can Tho, 2017
WORKS TO BE DONE IN
CAN THO UNIVERSITY
The scientific guidance: Assoc. Prof. Dr. Truong Thi Nga
The thesis will be defend against the council state thesis meeting at the:
At ……. time ……. day ………. month …… year ……..
Reviewer 1:
Reviewer 2:
Reviewer 3:
Thesis can be found at:
Learning resource center of Can Tho University.
National library of Vietnam.
1
The published articles in Journals of Science
1. Vo Nguon Thao, Huynh Trong Khiem and Truong Thi Nga, 2013.
The environmental factors and nitrogen forms in Ong Trang hillock,
Ca Mau province. Journal of Science, Can Tho University. Vol. 29a:
37-44.
2. Vo Nguon Thao, Nguyen Vu Minh and Truong Thi Nga, 2015. The
habit of eating three kinds of mangrove leaves, nutrient content in
mangrove leaves and feces of Sesarma sp. in Ca Mau province.
Vietnam Science and Technology. Vol. 2(9): 27-32.
3. Vo Nguon Thao, Truong Thi Nga, 2015. Litterfall production
assessment of Bruguirea parviflora, Rhizophora apiculata and
Avicennia alba in Ong Trang hillock in the Vien An commune, Ngoc
Hien district, Ca Mau province. Journal of Science, Can Tho
University. Special issue: Environment and Climate change: 1-8.
2
Chapter 1: INTRODUCTION
1. The significance of the dissertation
Mangroves are the world's most productive and unique wetland ecosystems in
intertidal regions of the tropical and subtropical coasts (Nagarajan et al., 2008;
Estrada et al., 2014). Mangrove plant growth and development on alluvial land
directly are affected by the tide, hot and humid climate, and regularly flooded
condition with high salinity. Hence, the existence and development of mangroves are
closely linked to climate factors, hydrology, topography, soil chemical and physical
characteristic which related on the top soil.
In terms of mangrove ecosystems management and sustainabldevelopment,
biodiversity planning and conservation, coastal reforestation, studies on internal
processes and external impacts to the ecosystem are requested. The diverse and
irregular impacts of environmental factors are likely causes of damage to the
mangroves.
At the moment, mangroves are facing to degradation and reduction in area due
to deforestation for shrimp farming and industrial zones. This ravages was the result
of the population growth, the absence of sense of community regarding the role and
functions of mangroves. On the other hand, the limited knowledge of the authorities
concerning the role of mangroves in providing mangroves soil with nutrition based
on forest animal acitivities, literfall and the decomposition of soil in mangrove
forest..
The study of forest structure according to environmental factors and litter fall
productivity, as well as nutrition research in the mangroves are urgently requirement
to serve as scientific and practical outcomes of strategic proposal in community
education, management, protection and sustainably use of mangroves.
2. Objectiveive of the dissertation
* General objective
Study the relationship of natural environment factors and the mangroves
ecosystem at Ong Trang islet in order to contribute to biodiversity conservation,
ecosystem preservation, sustainable development of mangroves under tidal influence
of the East sea and the West sea, and climate change response.
* Specific objectives
- Analyze the influence of soil environment factors and tide characteristics on
the distribution of mangrove.
- Identify characteristics of top soil and structural characteristics of mangroves
on Ong Trang islet.
- Assess litterfall yield, leaf decomposition process of the Avicennia alba,
Rhizophora apiculata and Bruguiera parviflora species at 3 top soil types on Ong
Trang islet.
3
- Sesarmid species identification; the leaf species and status consumption
choice of Sesarmid and their contribution on nutrient recirculation.
3. Dissertation structure
The dissertation in divided into 05 chapters: Chapter 1: Introduction; Chapter
2: Literature review, Chapter 3: Research methodology; Chapter 4: Results and
Discussion; Chapter 5: Conclusions and Recommendations.
4. Dissertation initiative
The study indicated the environmental factors influence the distribution of
mangroves on Ong Trang islet involved the topography, the tide movement, and
waterdepth, the physical and chemical characteristics of soil, such as N% changed
0.24%; P2O5% was 0.08-0.11%; organic matter was 10.09-10.7%, the salinity ranged
19,7‰. These environmental factors suitable for mangrove with 12 wood species, 4
bushes and weed species.
The reseach determined 3 kinds of top soil in the mangrove on Ong Trang islet:
Bruguirea parviflora at the tip, Rhizophora apiculate at the middle and Avicennia
alba at the end. At the end of the islet, the top soil characterized by the loam and silt,
deep submerged, reduction in soil , medium nutritional content of soil, rich in
organic matter The Avicennia alba species was the dominant species. At the middle
of Ong Trang mangrove, the Rhizophora apiculate species was dominant with the
typic top soil which had medium content of silt, loam and sand, quite good
nutritional content of soil and high organic matter. At the tip, Bruguirea parviflora
was adapted with the top soil characterized by the silt, loam and sand, a few the tide
movement, quite good nutritional content of soil and rich in organic matter.
In research on litterfall yield, the thesis assessed the highest nutritional
contribution of Rhizophora apiculate species, the annual dry weight of litterfall was
12.98 tons/ha/year, include litter leaf was 0.696 tons/ha/year, Nitrogen was 4 kg/ha,
Phosphate was 1 kg/ha and Carbon was 258 kg/ha. The time for half decomposition
of 3 species leaves from 71 to 86 days. The Avicennia alba leaves had the fastest
decomposition time. Leaves decomposition had meaning in nutrional contribution
for mangrove.
4 Sesarmid species were identified on 3 typics top soil in the mangrove, and
Perisesarma eumolpe was the dominant species. These species consumed all three
kinds of leaves: Bruguiera parviflora, Rhizophora apiculate and Avicennia alba.
These important results emphasis the important role of mangrove and Sesarma sp. in
the nutrient cycle of mangroves forest and Sesarma sp. is one of the important link in
the food web of mangrove forests. Sesarma sp. is not only affect to structure but also
physical and chemical characteristics of vegetation through burrowing to increase
noncohesiveness and aerobic properties of soil,… which their living activities impact
on the growth and development of plant and microorganism in soil.