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Natural Conditions of the Study Area


Chapter 3

BASIC CONDITIONS OF THE STUDY AREA

3.1. Natural conditions of the research area


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Natural Conditions of the Study Area

Figure 3.1. Map of Ba Vi National Park


3.1.1. Geographical location

Ba Vi National Park is located in geographical coordinates: From 20 0 55' to 21 0 07' North latitude.

From 105 0 18' to 105 0 30' East longitude.

- To the North are the communes of Ba Trai, Ba Vi, Tan Linh of Ba Vi district - Hanoi.

- To the South are the communes of Phuc Tien and Dan Hoa of Ky Son district - Hoa Binh.

- To the East are Van Hoa and Yen Bai communes of Ba Vi district - Hanoi; Dong Xuan communes of Quoc Oai district - Hanoi; Tien Xuan, Yen Trung, Yen Binh of Thach That district - Hanoi; Yen Quang commune of Ky Son district - Hoa Binh.

- To the West are Minh Quang and Khanh Thuong communes of Ba Vi district - Hanoi; Phu Minh commune of Ky Son district - Hoa Binh.

3.1.2. Terrain - topography

Ba Vi is a medium and low mountainous area, hills and mountains bordering the semi-mountainous area, this area can be considered as a mountainous area emerging in the middle of the plain, only 30 km south of the confluence of the Da River and the Red River. The three highest peaks are Vua Peak (1,270 m), Tan Vien Peak (1,227 m), Vien Nam Peak (1,028 m) and Ngoc Hoa Peak (1,131 m). There are also peaks such as: Hang Hum Peak (776 m), Gia De Peak (714 m).

Ba Vi mountain range consists of two main storm bands:

- The East-West thunderstorm strip from Oi stream to Lat bridge through Tan Vien peak and Hang Hum peak is 9 km long.

- The storm strip in the Northwest - Southeast direction from Yen Son through Tan Vien peak to Quyt mountain is 11 km long. And continues to Vien Nam to Zinc slope.

In general, Ba Vi is a fairly steep mountainous area, the western slopes fall down to the Da River, steeper than the northwestern and southeastern slopes, the average slope of


The area is 25 0 , the higher the slope, the more steep, from 400 m and above, the average slope is 35 0 and there are exposed cliffs.

3.1.3. Soil geology

This area was formed by the Idoxini orogeny 150 million years ago.

The parent rock composition distributed in the Ba Vi area is very rich and diverse, including the following main types of rock: Metamorphic rock, limestone, sedimentary - igneous rock, sedimentary rock, and unconsolidated rock.

About soil: The main soil of Ba Vi mountain range is formed on two main types of rocks, which are shale and sandstone, with the following main soil types: Yellow Feralit soil, yellow-brown Feralit soil developed on shale, sandstone, red-yellow Feralit soil developed on shale, sandstone, mica shale and other types of sedimentary rocks, ancient alluvial soil.

3.1.4. Hydro-climatic characteristics

The hydro-climatic characteristics of Ba Vi are determined by latitude, monsoon mechanism, and terrain.

Ba Vi area is located at latitude 21 0 North, affected by the monsoon mechanism, the combined impact of latitude and monsoon creates a humid tropical climate with a cold and dry winter, from coste 400 and above there is no dry season. The high terrain receives easterly winds so the rainfall is quite abundant and unevenly distributed in the area.

a. Thermal mode

The average annual temperature is 23.30 0 C, the coldest month is January (16.52 0 C), the hottest month is July (28.69 0 C).

The hot season is from April to November, the average hot season temperature is 26.1 0 C), the hottest day of the season can reach 38.2 0 C.


Cold season from December to March of the following year, the average cold season temperature is 17.9 0 C, the lowest temperature can drop to 6.5 0 .

b. Humidity mode

Humidity conditions are determined by the correlation between two opposite processes of rainfall and evaporation. Ba Vi has two distinct seasons: hot and humid season (from mid-March to mid-November) and cold and dry season (from mid-November to mid-March of the following year). At an altitude of 400 m, there is almost no dry season, because evaporation is always lower than rainfall.

Based on the classification of humidity and heat regime (Thai Van Trung), Ba Vi is classified as slightly humid to humid.

c. Rain mode

Annual rainfall is relatively large, unevenly distributed between regions. The high mountain area and the eastern slope have a lot of rain 2,587.6 mm/year, the area around the foot of the mountain has moderate rainfall 1,731.4 mm/year, the eastern slope has more rain than the western slope. The number of rainy days at the foot of Ba Vi mountain is relatively high, from 130 - 150 days/year, at the coste 400 m, the number of rainy days is quite heavy from 169 - 201 days/year, the average is 189 days/year.

+ Seasonal rainfall distribution is uneven throughout the year, every year there is an alternation of a heavy rain season and a period of little rain. During the rainy season, monthly rainfall > 1,000 mm lasts for 6 months, from May to October at the foot of the mountain and 8 months from March to October from the 400 m altitude and above, this rainfall accounts for more than 90% at the foot of the mountain and 89% at the 400 m altitude of the whole year's rainfall. Heavy rain from 300 - 400 mm/month is concentrated in the months of June, July, August (foot of the mountain) and the months of June, July, August, August, September at the 400 m altitude, the period of little rain lasts from November to April of the following year (foot of the mountain) and from November to February of the following year (400 m altitude), each month has from 5 to 10 rainy days.


d. Evaporation capacity

The evapotranspiration capacity in Ba Vi is about 861.9 mm/year to

759.5 mm/year, evapotranspiration is less variable in space than rainfall, evapotranspiration increases in the hot season by 80 mm/month and decreases in the cold season by 57 mm/month.

e. Moisture potential

Humidity potential is reflected through the humidity index calculated for the whole year. The humidity index of Ba Vi area varies from 2.0 (foot of the mountain) to 3.4 (mountainside), meaning that the rainfall is 2.0 to 3.4 times greater than the water demand of the vegetation. In terms of humidity potential, this area is basically tropical humid but has a cold, dry winter, so the climate of this area is not a typical tropical climate, but a mixed climate, thus creating conditions for the rich and diverse development of the flora here, with both tropical and subtropical plant species.

3.1.5. Other factors to consider

a. Air humidity

Air humidity increases with altitude and especially above 1,000 m altitude, air humidity is almost humid all year round, 92.0% highest in early summer (March, April, May).

b. Dry and hot westerly wind

Every year in May, June, and July, there are often dry and hot westerly winds, accompanied by sunshine, which greatly affect the seedlings in the nursery. On average, for all 3 months, there are 15 to 18 dry, hot days with high temperatures exceeding 35 0 C and low relative humidity < 50%.

c. Frost

On cold winter nights, the air temperature in Ba Vi area can drop to 0 0 C, while the surface temperature often drops below 0 0 C water vapor.


In the air, ice crystals sublimate into tiny ice crystals, creating frost. The water in plant cells freezes, the volume of water in the cells increases, breaking the cell structure, making nursery stage plants susceptible to mass death.

The frost situation in Ba Vi area can be considered "mild" compared to the mountainous and midland areas of the North.

d. Thunderstorms and hail

Due to the influence of the high Ba Vi mountain range, it creates a "lightning center" during the rainy season. Every year, there are about 70 thunderstorm days in each area, with the strongest thunderstorm activity occurring in the months of May, June, and July.

Associated with thunderstorms are strong winds called gusts that last only 15 - 20 minutes, thunderstorms can cause hail.

3.1.6. Hydrology

The Da River flows along the west side of Ba Vi Mountain, the highest annual water level is < 20 m and the lowest annual water level is 7.7 m (1,971) above sea level. Apart from the Da River, the Ba Vi area has no large rivers or streams, most of the streams are small and steep. In the rainy season, the large amount of water flows rapidly, causing soil and rocks to fill many fields at the foot of the mountain, breaking many dams of small hydroelectric stations. On the contrary, in the dry season, there is very little water and the streambed dries up.

In the area there are 8 artificial lakes such as Dong Mo Ngai Son Lake, Hooc Cua Lake, Suoi Hai Lake, Xuan Khanh Lake, Da Chuong Lake, Minh Quang Lake, Che Lake and Phu Minh Lake.

3.1.7. Forest resources

a. Current status of land types and forest resources

The total area of ​​forestry land managed by the National Park is: 10,814.6 ha, of which:

- Forested area: 8,188.0 ha, accounting for 75.7% of the park area


+ Natural forest area: 4195.5 ha, accounting for: 51.2% of forested area

+ Area of ​​planted forests of all kinds: 3992.3 ha, accounting for 48.8% of forested area.

- The area of ​​land without forest is: 2386.7 ha, accounting for: 22.1% of the area of ​​the Park.

- Other land types are: 240.1 ha, accounting for 2.2% of the garden area.

(Details of current land use planning by functional area and by province - appendix).

Thus, Ba Vi National Park has a large forest ratio, in which the natural forest area accounts for 51.2% of the forested land area, here there are nearly 1,000 hectares of primary forest that is less affected. However, the area of ​​land without forest is 22.1%, it is necessary to be zoned for regeneration combined with additional afforestation and new afforestation to restore the forest ecosystem, promoting the functions and tasks of the Park.

b. Forest vegetation

Vegetation in Ba Vi National Park area includes 3 main types:

- Type of closed broadleaf evergreen subtropical humid lowland forest.

- Mixed evergreen closed forest with broadleaf and lowland subtropical conifers.

- Type of closed broadleaf evergreen tropical lowland humid rainforest:

+ Bamboo forest: The presence of the giang forest population is the result of the process of over-exploitation or the process of burning down the forest to make fields by people living around the mountain in the past. Giang often grows into dense bushes stacked on top of each other to form a closed and low canopy, limiting the regeneration ability of woody species.

- Recovered forest: This is a population that appears after abandoned fields on good land. This type of forest is distributed in concentrated patches around mountains from an altitude of 100-500m. This population has a simple structural form with


A fairly uniform canopy layer of trees, a type of forest of the same age and consisting of pioneer species such as Ba soi (Macaranga denticulata), Hu day (Trema angustifolia), Ba bet (Mallotus apella), a small diameter population of 8 - 10 cm, low height of 8 - 10 m, relatively dense, in addition to the following species: Muoi (Rhus chinensis), Mang tang (Litsea citrata), Ngoa long (Ficus julva), Co ke (Grewia paniculata), Thoi ba (Alangium sinesis). This is a type of forest in succession, if well protected, it can return to the original sub-region or sub-soil type.

- Planted forests: Main tree species include: Acacia, Pine, Camphor, Rosewood, Black Cassia, Canarium, Crocus, Rhizome, Euryale... Trees that grow well are mainly planted on the slopes and foothills of Ba Vi mountain range.

c. Forest flora

Ba Vi has tropical and subtropical climate zones at altitudes from 100 -

1,296 m, so the forest flora is quite rich, with both tropical and subtropical plants.

Plant species composition: According to documents from "Flora of Indochina" by French botanist Lecomte (1886 - 1891) and after 1954. According to the catalog of many domestic and foreign botanists who collected samples and studied the flora of Ba Vi area, along with the initial results of the investigation of the flora of the extended area of ​​the Forestry University, in Ba Vi there are 1,209 species of higher plants belonging to 633 genera and 157 families.

There are some notable groups of plants:

- Rare plants: There are 36 species.

- Ba Vi endemic plants have 49 species.

- 15 species of trees have valuable timber.

- Multipurpose tree has 20 species.

- 668 medicinal plant species.

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