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Chapter 4. RESEARCH RESULTS AND DISCUSSION
4.4. Characteristics of geographical factors in the vegetation on the
limestone mountain in Cam Pha city, Quang Ninh province
The vegetation on limestone mountain in Cam Pha city were
effected of the characteristics of Asia tropical flora, which has the
mixture nature of many plant types. Compared to the flora of Vietnam
(20 plant geographic factors), the flora on Cam Pha limestone mountain
only lacks 2 elements: Central endemic element and Southern endemic
element. The diversity of plant geographic factors of limestone
mountain flora in Cam Pha city plays a very important role for
landscape ecology and geological and geomorphological values.
4.5. Characteristics of vegetation structure on the limestone
mountains in Cam Pha city, Quang Ninh province
4.5.1. Characteristic of structure
- Vegetation in limestone mountain valley:
Research results at plots in Buom island, Vung Gieng island, etc.
show that, in 25 plots, 42 species of timber trees participate in the
formula of composition, in each plot the dominant woody species range
from 4 to 8 species.
Figure 4.3. The vegetation in limestone mountain valley in Cam
Pha city (2016)
Note: Shl-Sung Ha Long; Trbđ- Tra bo đe; Trq- Trom quy; Vđmc- Vong đo mun coc;
Vg- Vai guoc; Sa- Sang; Sqnh- Si qua nho; Sb- Sung bau; Sltr- Soi la tron; Trli- Trai li;
Bbnh- Ba bet nhung;Blnh- Boi loi nhot; Ngph- Ngai phun; Ngml- Ngoai moc la; Sgđ- Sung
gan đung; Chth- Cheo thuc; Mc- Mang cut;Thm- Thung muc.
- Vegetation at the down of limestone mountain:
The results show that, of total 25 plots surveyed in Beo Cay Ngo,
Ong Be Con,... there are 49 species of plants participating in the
formula of composition, in each plot the dominant tree species range
from 4 to 9 species.
Figure 4.4. The vegetation in limestone mountain foot in Cam Pha
Note: Blnh- Boi loi nhot;Sltr- Soi la tron;Sa- Sang;Mt- May teo; TrbđTra bo đe; Trlch- Tra lam chieu;R- Rang; Vc- Vong cach; St- Son ta;SiqnhSi qua nho; Gi- Gia; Đm- Đon mong; Thmđ- Thien mon đong; Thh- Thanh
Huong; Đo- Đom; Phđ- Phen đen.
- Vegetation on cliff slopes:
The combined results from the survey lines on Cay May island,
Cu Cai island and Cai Bua island,... show that of total 18 investigated
routes, 31 species participate in the formula of composition, in each
investigated routes dominant tree species range from 3 to 6 species.
Figure 4.5. The vegetation on the limestone cliff slopes in Cam Pha
Note: Gnb- Gang nam bo;Sa- Sang; Siqnh- Si qua nho; So- Sop;Thh- Thanh Huong;
Sltr- Soi la tron; Trq- Trom quy; Sung gan đung; Ma- Mang; Vđmc- Vong đo mun coc;
Shl- Sung ha long; Ngbhl- Ngu gia bi ha long;Qg- Quyt gai; Bm- Bong moc.
4.5.2. Characteristics of density structure
The results show that the vegetation at the down of mountain has
the highest density (8,410 trees/ha), 1.6 times higher than the
vegetation in the valley and 20 times higher than the vegetation on the
cliff slope. The vegetation on the slopes and cliffs has the lowest
density of trees (413 trees/ha).
4.5.3. Structure N/D1.3
The N/D1.3 distribution alignment according to three common
theoretical distributions, like Distance, Meyer and Weibull was tested.
As test with Weibull function, 24/25 plots hypotheses H 0 were
accepted, so Weibull function is the best simulation function of N/D 1.3
structure for the vegetation of limestone mountain valley in Cam Pha city.
4.5.4. Structure N/Hvn
The results show that, when test with Weibull function, 22/25 plots
hypotheses H0 were accepted, so Weibull function is the best simulation
function of N/Hvn structure for the vegetation of limestone mountain
valley in Cam Pha city.
4.5.5. Rules of correlation between height and diameter (H vn/D1.3) in
the vegetation of limestone mountain valley in Cam Pha city, Quang
The analytical results show that only Power function is suitable to
simulate Hvn/D1.3 correlation, with the highest R2 coefficient ranging
from 0.4 to 0.958.
4.6. Growth ability of woody trees in the vegetation on the limestone
mountains in Cam Pha city, Quang Ninh province
4.6.1. Growth capacity of woody trees in vegetation on the limestone
mountains in Cam Pha City according to diameter variation (D1.3)
The diameter data (D1.3) of the woody tree were analysed by R
software, the results are shown in Table 4.13.
Table 4.13. Results of estimating parameters of
growth function for diameter (D1.3)
The results show that the correlation coefficient R2 of the functions
is equivalent (0.995), so Gompertz, Johnson-schumacher and Verhulst
functions describe well the growth rate of the trunk diameter in the
vegetation on the limestone mountains in Cam Pha city.
4.6.2. Growth capacity of timber trees in the vegetation on the
limestone mountains in Cam Pha city, Quang Ninh province, according
to the variable of the height (Hvn)
Completely similar to diameter variable, data measured from
PLOT, surveyed lines and data inherited from bay management over
the years are used to analyse nonlinear correlation for Gompertz,
Schumacher and Verhulst. The analytical results are shown in the
Table 4.16. Parametric equations simulating the height (H vn)
The results show that all three growth functions are well simulated
for the height growth according to age. Based on that, three growth
functions including Gompertz, Schmacher and Verhulst were used to
simulate the growth for the variables of diameter and height of woody
trees in the limestone mountain vegetation in Cam Pha city.
The results show that all three functions can simulate well the
growth of forest trees in the study area. Correlation coefficients for
both diameter variable and height variable are very high (0.995).
However, if considering more accurately, the Schumacher function has
the highest compatibility, because the AIC value is the lowest in the
three models, which is true for both diameter and height variables. All
parameters of the regression model exist in the whole, since the Pr
values are much less than 0.05. This shows that the models are really
meaningful and can be applied to other areas with the same
characteristics of plants and other natural conditions.
4.7. The regeneration capacity of timber trees in the vegetation on
the limestone mountains in Cam Pha city, Quang Ninh province
4.7.1. The structure and density of regenerated woody trees
The results show that the number of regenerated tree species
appearing in the vegetation of limestone mountain valley is 40 species,
of which 4 species participate in the formula of composition such as
Ficus alongensis, Ficus microcarpa, Litsea glutinosa, Sterculia
lanceolata (Vung Gieng island, Cay Nua island, Cua Vong island), in
which Ficus alongensis is the species that accounts for the highest
proportion of 11,16%.
4.7.2. Origin and quality of regenerated woody trees
The survey results on the quality and origin of regenerated trees in
limestone mountain vegetation in Cam Pha are shown in Table 4.20.
Table 4.20. The origin and quality of regenerated
woody trees in limestone mountain vegetation in Cam
Good Medium Bad
In the valley
2938 2304 78.45 634 21.6
At the foot of
3880 2898 74.7 982 25.3
On the cliff
612 74.65 208 25.3
2546 1938 76.24 608 23.8 45.7
The table shows that regenerated seedlings vary from 74% to 78%, on
average of 76%.
4.7.3. Distribution of regenerated woody trees according to the height
Distribution of regenerated timber tree according to the height is
presented in Table 4.21.
Table 4.21. Distribution of regenerated timber trees according to
the height in limestone mountain vegetation in Cam Pha City
Number of regenerated trees according to the
height (No. of tree/ha)
<50 cm 50-100 cm 100-150 cm >150 cm
In the valley
At the down of
On the cliff
The results showed that the density of regenerated trees was the
highest at the height of <50 cm, range from 820 to 3880 trees/ha, on
average of 2546 trees/ha. At the height of 50-100 cm, the density of
regenerated trees varies from 368 to 1475 trees/ha, on average of 1018
trees/ha. At the height of 100-150 cm, regeneration density varies from
213 to 1264 trees/ha, on average of 812 trees/ha. The lowest density
observed at height level > 150 cm, regeneration density varies from 145
to 798 trees/ha, on average of 496 trees/ha.
4.7.4. Distribution of regenerated timber trees in horizontal plane
Results of distribution of regenerated woody trees are summarized
in the following table:
Table 4.22. Distribution of regenerated woody trees in
1 Vegetation in the valley
Vegetation at the down
Vegetation on the cliff
The table shows that the distribution of regenerated timber trees in
the valley vegetation is random. The distribution of regenerated timber
trees in vegetation at the foot of the mountain and cliff slopes is
distributed in clusters. This distribution is consistent with the terrain of
limestone mountain. The vegetation in the valley has relatively flat
terrain and thick layer of soil, so when the fruits and seeds fall down,
they are distributed randomly on the ground. For vegetation at the
down of mountains and cliff slopes, due to steep terrain, when fruits
and seeds fall down, they tend to slip to the same position leading to
the regenerated trees distributed in clusters.
4.7.5. Factors affect the regeneration capacity of seedlings
188.8.131.52. Effect of terrain factors
The results on the influence of limestone mountain topography on
the quality and density of regenerated trees are shown in the following
Table 4.24. Effect of topographic factors on the regeneration capacity of
trees in the vegetation on the limestone mountains in Cam Pha City
Foot of mountain
100-150 Down of
>150 cm Valley
The quality of regenerated trees
SL TL (%) SL TL (%) SL TL (%)
Topography affects regenerating woody trees through ecological
factors such as temperature, humidity, light, soil.
The limestone mountain topography in Cam Pha city affects the
density and quality of regenerated trees. In addition, due to the
specific terrain conditions, such as the steep rocky terrain, the
terrain factor also affects regenerated trees through the germination
rate of seeds. Therefore, it is necessary to apply technical measures
to improve the germination rate and survival capacity of regenerated
trees in the future.
184.108.40.206. Influence of human factors
Human impact on the regeneration capacity of the vegetation on
the limestone mountains in Cam Pha city through mineral exploitation,
exploitation of timber, firewood and non-timber forest products:
- Timber and firewood exploitation: timber and firewood on
limestone mountains has good quality. So, firewood exploitation
activities is still taking place in some limestone mountains near
- Exploitation of medicinal plants: Species of medicinal plants are
strongly exploited as Pleomele cochinchinensis Merr., Tinospora
sinensis, Stephania rotunda Lour.
- Exploitation of ornamental plants: Species are exploited such as
Cycas tropophylla, Ficus pumila, Ficus benjamina L.,... those are
endemic species named in the red book.
4.8. Evaluate and summarize the value, management and use
situation and identify the risks of degradation of vegetation on the
limestone mountains in Cam Pha city, Quang Ninh province
4.8.1. The value of vegetation on the limestone mountains in Cam
Pha city, Quang Ninh province
220.127.116.11. Scientific value
- In 1962, Ha Long Bay was ranked by the Ministry of Culture and
Information as scenic national monument. In 1994, Ha Long Bay was
recognized as a World Natural Heritage Site by UNESCO, because of
its exceptional value and global in landscape. In 2000, once again, Ha
Long Bay was recognized as a world natural heritage by UNESCO
with special value on geomorphological geology. In particular, Cam
Pha limestone mountain area is the buffer zone of Ha Long Bay.
Therefore, the vegetation on the limestone mountains in Cam Pha city
plays a big role in creating this landscape value.
- Endemic species: Flora on the limestone mountains in Cam Pha
city has 16 endemic species of plants of Vietnam. Of them, there are 12
narrow endemic species (those only appear on Cat Ba, Ha Long and
Cam Pha islands) and 4 species are endemic species of Northeastern
- Rare and precious species: On the rocky mountains in Cam Pha,
27 rare and precious plant species are recorded. 22 species of plants
was listed in the Vietnam Red Data Book (2007), in which there was 1
species at Critically Endangered (CR), 7 species at Endangered (EN),
14 species at Vulnerable (VU). 7 species are listed in the Appendix of
Decree No. 32/2006-NDCP. 6 species belongs to Appendix IIA
(limited to exploitation for commercial purposes). At the international
level, there is one species ranked Near Threatened (NT).
18.104.22.168. Economic value
The survey results determined the use value of the plant species
including the following groups:
- Group of trees for fuelwood:
There are 11 species of timber value, accounting for 1%, they are
small and medium timber species growing on rocky mountains or some
large timber species are acclimatized from the mainland.
Currently all woody tree species on the limestone mountains have
been protected from deforestation exploiting wood or burning charcoal.
- Group of medicinal plants:
Statistical results show that 471 species can be used as medicine,
accounting for 77.4% of total species. This ratio shows that the
vegetation in the study area has many medicinal plants which play an
important role in the system.
- Group of ornamental plants:
There are 253 species in this group, accounting for 16% of the
total species. In which, the family having the most ornamental species
belong to Orchidaceae (15 species) and then Arecaceae (17 species).
- The group of plants taking essential oils
Statistic study 26 species accounting for 1.6% of total species. 12
species of essential oil plants have been recorded in Bai Tu Long bay.
- Plant group supporting agriculture: one species that supports the
agriculture is Wrightia laevis Hook.f..
- Plants producing latex: On the limestone mountains in Cam Pha
city, there is 01 species poducing latex. That is Toxicodendron
succedanea (L.) Nold..
- Fiber plants: On the limestone mountains in Cam Pha city, there
are 02 species of fiber plants used to make traditional paper, they are
Gio day (Rhamnoneuron balansae (Dranke) Gilg.) and Niet gio
(Wikstroemia indica (L.) C.A. Mey.).
22.214.171.124. Environmental value
- The vegetation on the limestone mountains is effective against
limestone erosion, plant wastes in the vegetation create humus soil
layer on limestone mountains.
Humus layer plays an important role in moisturizing and is a living
environment for other organisms. Limestone mountain vegetation is also involved
in climate regulation, environmental cleanup.
- The vegetation on the limestone mountains is like a shield,
reducing the impact of storms.
126.96.36.199. Landscape value
- The vegetation on the limestone mountains with an average
height of 1-2 m, stems have many specific shapes of plants on rocky
mountains. Therefore, the vegetation on the rocky mountain has
contributed to adorn the landscape of limestone mountains.
- The vegetation also has the effect of keeping water in caves,
creating an interesting image effect of limestone cave landscape.
4.8.2. Situation of management and conservation of vegetation on the
188.8.131.52. Agencies involved in managing the vegetation on the limestone
mountains in Cam Pha city
- In terms of state management: Each commune has a official
assisting the chairman of the commune People's Committee to manage
forestry development in the commune.
- In terms of expertise: Bai Tu Long Bay Management Board is a
professional agency to help Cam Pha City People's Committee manage,
preserve and promote the value of vegetation on the limestone
mountains. Bai Tu Long Bay Management Board has 46 staffs.
184.108.40.206. Documents, policies to direct the implementation of
Decision 1798/QD-UBND approving the Environmental Planning
of Halong Bay to 2020, vision to 2030 as a basis for managing the
ecological environment of Ha Long Bay (including the buffer zone);
Resolution 68/NQ-HDND of Quang Ninh People's Council on the
management, conservation and promotion of world natural heritage
values in the period of 2013-2015, vision to 2020;
Plan No. 92/KH-QLVHL on the implementation of the action
program, implement of Resolution No. 68/2012/NQ-HDND of
12/12/2012 of the Provincial People's Council on the management,
conservation and promotion of world nature heritage values of Ha Long
Bay in the period of 2013-2015, vision to 2020.
220.127.116.11. Analysis results of the conservation of vegetation on the
limestone mountains in Cam Pha city
- The number of violations of Bai Tu Long Bay management and
The number of violations decreased over the years, there were 57
violations in 2010, and 18 violations in 2016. Of the 241 violations
from 2010 to 2016, all were administratively handled, showing the
level of violations was only on a small scale.
The violation rate is 0.03 case/ha (241/6466). Thus, the situation
of people's violation for the limestone mountain vegetation is not
alarming; the limestone mountain vegetation has weak structure, so it is
still necessary to have more effective solutions to reduce the number of
- Interview results of household and individuals:
Conducting interviews with 30 households living in mainland and
sea in wards of Quang Hanh, Cam Thinh, Cua Ong, Cam Binh, and 30
individuals who are staffs of the Bay Management Board, staffs
working at ward and commune, forest rangers staffs. Interview results
are summarized in the table 4.30:
Table 4.30. Summary of interview results on the impacts of people
on the limestone mountain vegetation
Ornamental plant exploitation
Medicinal plant exploitation
Exploitation of non-timber forest
The results of interviews with people and staffs showed that the
number of answers with exploitation of medicinal plants accounted for
the highest proportion (People 33%; Staffs 12%), followed by the
number of answers with ornamental plant exploitation (People 23%;
Staff 6%). The number of answers with other impacts is low. This
shows the impacts of people on the limestone mountain vegetation in
Cam Pha at a low level.
- The results of SWOT analysis show the advantage in the
management of conservation is the vegetation on the limestone
mountains in Cam Pha city belonging to the buffer zone of Ha Long
bay (twice recognized by the UNESCO for geomorphological
Because of this importance, the limestone mountain vegetation in
Cam Pha city has a specialized agency to manage, called the Bai Tu
Long Bay Management Board.
Currently, the number of staffs in Bai Tu Long Bay Management
Board is 60. However, the quality of staff is still limited, failing to meet
the task requirements in conservation. So, the work of conservation of
vegetation on the limestone mountains has many opportunities and
4.8.3. The risks of degradation of limestone mountain vegetation in
Cam Pha city, Quang Ninh province
Applying the evaluation method of Ngo Dinh Que (2011), we
conducted survey of 50 plots (area of 2500m2/plot) in the vegetations in
valley, at the down of mountain and 18 survey lines (5m wide and 50m
long) in the vegetationat on the cliff slopes.
Results show that the down of mountain and valley vegetations
has similar degradation level, over 70% of plots studied have low
degradation level, 16-20% of plots have degradation level at average,
8% of plots have serious degradation level, and no PLOT at very
serious degradation level. The vegetation on the cliff slopes has 67% at
average level of degeneration, the remaining 33% of studied routes has
serious degradation level. All three vegetations do not have any plot or
studied routes at very serious level of degradation.
The vegetation in the valley and the down of the mountain are at a
low degradation level, the vegetation on the cliff slopes is at moderate
degradation level. In general, limestone mountain vegetation in Cam
Pha city is not at an alarming level of degradation. The vegetation