vegetation zones of Nepal
Nepal can been divided into six ecological zones, with one of them divided into two sub-zones. they are:
- Terai;
- Chure;
- Inner Terai;
- Lesser Himalaya:
- Mahabharat Range;
- Midlands;
- Higher Himalaya;
- Trans-Himalaya.
factors governing distribution of vegetation in Nepal
in the Nepal the vegetation bands are relate broadly to altitude. the main factors, which govern the distribution of vegetation, are:
- altitude;
- aspect;
- rainfall and its distribution;
- geology and soils (relatively minor scale).
vegetation zones
although the classification of vegetation types is based primarily on altitude, we must not think that the altitudinal zones described are rigid. many tree species occur over a wide range of altitudes, and though they may predominate in a particular zone, they may also occur in zones above and below it. for example, gobre salla (Pinus wallichiana) has its main range from 1800 metres to 4000 metres, but it may occur 80 or 100 metres below this level.
where two vegetation zones meet there is a transitional zone where species from both zones occur.
the following lists provide some examples of the vegetation types found in the different zones.
Tropical zone: upper boundary at about 1000 m
- sal forest;
- khayer + sisau forest;
- other riverain forest;
- grassland;
- asna forest (Terminalia spp.).
sub-tropical zone: range 1000 - 2000 m in the west and 1000 - 1700 m in the east
- khote salla;
- chilaune + katus;
- utis;
- riverain forest (tooni + siris).
lower temperate zone: range 2000 - 2700 m in the west and 1700 - 2400 in the east
- khasru;
- gobre salla;
- banjh
- lower temperate mixed broadleaf forest.
upper temperate zone: range 2700 - 3000 m in the west and 2400 - 2800 m in the east
- banjh;
- gurans;
- upper temperate coniferous forest (gobre salla).
- upper temperate broadleaf forest;
sub-alpine zone: range 3000 - 4200 m in the west and above 3000 m in the east
basically forest species are found growing in the cool desert areas having a rainfall of less than 300 mm/year. small spiny shrubs are found in the Mustang and Dolpa areas. species include gurans, gobre salla and dhupi.
alpine zone: above the snow line
species include gurans, dhupi, thorny plants and shrubby species.
local species
we can only produce a list of the locally available species in an area by carefully examining it. these are some of the local species that are found within the Kurintar area:
trees: Sal, bhalyo, banjh, kavro, simali.
shrubs: Paineti, asuro, dhanyero, areri, dhusun
grasses: Sito, muse kharuki, kans.
some grass species found on roadside slopes in Nepal
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2500
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1000
500
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Phurke Sito Amliso Setaria Muse-kharuki Napier Khar Dhonde Kans Babiyo |
plant morphology and its role in bioengineering
there is vast diversity of plants with regards to the shape and size of their parts. You will look at the major types of roots, stems, and leaves, and will be able to find out their role in slope stabilisation. there are various types of roots: some are very deep and others are shallow, some have many lateral roots and others do not. obviously, each type will perform different types of engineering functions. similarly, strong and rigid, weak and flexible or creeping stems and the shape and size of leaves affect on controlling soil erosion and slope stabilisation depending on the environmental conditions of the site.
the terms: plant morphology, roots, and shoots
parts of plant
roots, rhizomes, and stolons
roots, rhizomes, and stolons are underground or on-the-ground parts of plants. basically, these are the plant parts that responsible for performing the engineering functions.
shoots - strong, weak, and creepers
shoot is the upper ground part of the plant. basically, they are the trunk, stems, branches, twigs, with leaves, flowers, and fruits. there area different types of stems of plants.
leaves - simple and compound, large and small
along with the morphological characteristics, there are other physical characteristics that have to be considered for the selection of bioengineering species. availability of the planting material is another important factor that has to be considered properly.
simplicity in regeneration
in bioengineering, a large amount of planting material is required. Kans, a grass commonly used in bioengineering is propagated by slips. a slip is a piece that is separated from a clumping grass so that it has shoots with buds and as much roots as possible. thousands of such slips may be grown in a nursery. therefore, only the species, which can be easily propagated by slips, can be regenerated with this method. There are other methods of propagation. they are:
· by seeds;
· by hard wood cuttings;
· by stem cutting; and
· by culm cutting.
remember that the species that are easily multiplied by any of these methods have to be considered for further use in bioengineering.
role of water and nutrient for plant life
role of water for plant life
water is one of the important life factors for the growth and development of plants. it is a solvent that dissolves all the minerals needed for the plants. plants these minerals from the soil solution. these minerals are transported from roots to leaves with the help of water. about 98% of water absorbed is transpired, and it is used for the transportation of minerals and less than 2% of water is used for the metabolic activities of the plants. therefore, plants use a lot of water to accumulate oraganic matter. based on the coefficient of transpiration (CT) the plants are categorised as:
· Hydrophytes - plants constantly living in water with CT above 900.
· Hygrophytes - plant requiring plenty of water with CT 600 - 900.
· Mesophytes - plants requiring sufficient water with CT 400 - 600.
· Xerophytes - plants adapted to the arid habitat with CT less than 400.
note: CT = amount (weight) of water absorbed/amount (weight) of organic matter accumulated
the water helps in transporting the organic matter produced in the leaves to other parts of the plant.
the water is necessary for the cell division and their development. the role of water for all the plant species is the same.
role of nutrients for plants
plants need at least 18 elements for their growth and development. they are C, O, H, N, P, K, Ca, Mg, S, Fe, B, Mn, Mo, Cu, Zn, Co and Cr etc. Carbon (C) are absorbed form the air in the form of Carbon dioxide. Basically the water absorbed by the roots is the raw material for Hydrogen and Oxygen all the other elements are absorbed by the roots from the soil in ionic forms. the quantitative requirement of plants in these elements is different. the elements which are required by the plants in large quantities are known as macro nutrients where as those which are required in low quantities are known as micro nutrients.
Nitrogen: it is one of the most important elements for the growth and development of plants. Nitrogen is the component of all the proteins and nucleic acids. all the Physiological activities are associated with enzymes which themselves are proteins. therefore Nitrogen deficiency cause:
· general chlorosis (yellowing) of plants.
· decrease in photosynthesis.
· retarded growth and development.
Phosphorus: it is another most important element. it is the component of nucleic acids, nucleoproteins, some vitamins and enzymes. Phosphorus compounds are the storage of energy. no metabolic activity can take place without energy that is supplied by the phosphorus compounds like ATP. Phosphorus deficiency causes:
· stunted growth
· late maturity
Potassium: Potassium doesn't make any organic compounds in the plants. it is found in the form of potassium ion or in the form of inorganic compounds in the cell. it maintains the colloidal status of cytoplasm. it increases the viscosity of cells and regulates the exchange of substances among the cells. Potassium causes:
· short inter-nodes.
· weak and twisted twigs and branches.
· burnt like leaf blades
Light: Light effects on structural development, food preparation, formation of flowers and fruits. the formation of green substance:- chlorophyll, responsible for photosynthesis is possible only in the presence of light. in dark plants developed a syndrome known as "etiolation" in which the formation of chlorophyll doesn't take place, the plants become very weak and turned yellow. Photosynthesis takes place only in the presence of visible light. the brightness of light is known as the intensity of light. based on the requirement of intensity of light for photosynthesis plants are grouped as:
· light liking plants:- requiring high intensity of light
· shade liking plants:- requiring low intensity of light
these characteristics of plant species have to be considered in selecting the appropriate species for bioengineering. it is specially important for the combination of trees, shrubs and grasses. in general low intensity of light slows down the photosynthesis and high intensity of light intensifies it in light liking plants but high intensity of light may cause s negative effect on photosynthesis of shade liking plants.
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