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Chapter 4. RESEARCH RESULTS AND DISCUSSION

Chapter 4. RESEARCH RESULTS AND DISCUSSION

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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.



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Figure 4.4. The vegetation in limestone mountain foot in Cam Pha

city (2016)



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

city (2016)

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).



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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

Ninh province

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)

Function

Gompertz

Johnson-schumacher

Verhulst

Parameter a

3-18

3-18

3-18

Parameter b0

13.521

19.368

12.805

Parameter b1

0.577

35.322

0.683

Parameter b2

0.041

37.572

0.056

R2

0.99507

0.995261

0.994921

AIC

-44.84719

-45.47957

-44.36834



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



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the years are used to analyse nonlinear correlation for Gompertz,

Schumacher and Verhulst. The analytical results are shown in the

following table.

Table 4.16. Parametric equations simulating the height (H vn)

Function

Parameter a

Parameter b0

Parameter b1

Parameter b2

R2

AIC



Gompertz

3-18

11.248

0.698

0.045

0.99501

-44.65503



Johnson-schumacher

3-18

17.043

37.017

33.084

0.995246

-45.42845



Verhulst

3-18

10.483

0.865

0.065

0.99479

-43.97494



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.



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Table 4.20. The origin and quality of regenerated

woody trees in limestone mountain vegetation in Cam

Pha city

Origin

Quality (%)

Location of

No. of

Per.

Per.

vegetation

tree/ha Seed

Shoot

Good Medium Bad

(%)

(%)

In the valley

2938 2304 78.45 634 21.6

49

30

21

At the foot of

3880 2898 74.7 982 25.3

58

26

16

mountain

On the cliff

820

612 74.65 208 25.3

30

45

25

slopes

Average

2546 1938 76.24 608 23.8 45.7

33.7

20.7



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

Location of

No. of

height (No. of tree/ha)

tree/ha

vegetation

<50 cm 50-100 cm 100-150 cm >150 cm

In the valley

2938

1211

987

546

194

At the down of

3880

1475

1264

798

343

mountain

On the cliff

820

368

213

145

94

slopes

Average

2546

1018

821

496

210

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



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horizontal plane

No.

Location

1 Vegetation in the valley

Vegetation at the down

2

of mountain

Vegetation on the cliff

3

slopes



λ

0.4408



r

0.84



U

1.39



Distribution type

Random



0.582



0.55



-2.07



Cluster



0.1231



0.19



-10.9



Cluster



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

4.7.5.1. 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:

Table 4.24. Effect of topographic factors on the regeneration capacity of

trees in the vegetation on the limestone mountains in Cam Pha City

Height



Terrain



No. of

tree/ha



Valley

1211

Foot of mountain

1475

Cliff slopes

368

Valley

987

Down

of

50-100 cm

mountain

1264

Cliff slopes

213

Valley

546

100-150 Down of

cm

mountain

798

Cliff slopes

145

>150 cm Valley

194

Down of

343

mountain

<50 cm



The quality of regenerated trees

Good

Medium

Bad

SL TL (%) SL TL (%) SL TL (%)

490

40.52

496

41.69

225

17.80

746

50.60

510

34.67

219

14.73

123

33.53 187

51.18

58

15.29

551

55.92 246

25.04

190

19.05

753

77

245



59.64

36.51

45.25



290

91

194



23.05

43.49

35.67



221

45

107



17.31

20.00

19.08



339

66

83

180



42.56

46.11

42.95

52.79



263

59

88

120



33.54

41.19

45.66

35.41



196

20

23

43



23.90

12.69

11.39

11.80



17

Cliff slopes



94



44



46.94



37



40.00



13



13.06



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.

4.7.5.2. 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

residential areas.

- 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

4.8.1.1. 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.



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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

Vietnam.

- 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).

4.8.1.2. 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..



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- 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.).

4.8.1.3. 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.

4.8.1.4. 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

limestone mountains

4.8.2.1. 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.

4.8.2.2. Documents, policies to direct the implementation of

conservation

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);



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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.

4.8.2.3. 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

conservation:

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

violation cases.

- 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

Impacts

Timber exploitation

Firewood exploitation

Ornamental plant exploitation

Medicinal plant exploitation

Exploitation of non-timber forest

products

Other impacts



Individual

No.

Per. (%)

1

3

5

16

7

23

10

33



No.

0

2

2

4



Official

Per. (%)

0

6

6

12



5



16



2



6



2



6



2



6



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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

landscape value).

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

challenges.

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



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