Types of Forest in Nepal

May 31, 2020 Gaurab Karki Biodiversity 0




Forest of Nepal

  • According to the forest act 1993 of Nepal, forest is defined as all the area, which is fully or either partially occupied by trees.
  • According to the International Center for Integrated Mountain Development (ICMOD), forest covers 57,538 km2 that contributes 39.09% to the total geographical area of Nepal.

Vegetation zone in Nepal

  • On the basis of levels of altitude and with different types of climate, Stainton described thirty-five types of forest in Nepal.
  • The forest of Nepal changes quickly owing to a great variation of topography, climate and soil conditions.
  • The forest of Nepal has been described here on the basis of the levels of altitude, and different types of climate under the following vegetation zones:
    1. Tropical zone(-1,000m)
    2. Subtropical zone (1,000-2,000m)
    3. Temperate zone (2,000-3,000m)
    4. Subalpine zone (3,000-4,100m)
    5. Alpine zone (4,100-5,500m)

TROPICAL ZONE:

  • This zone principally includes Terai, Bhabar, and Dun valleys.
  • It extends from east to west up to 1,000m and major vegetation types are Sal forest, Tropical deciduous riverine forest and Tropical evergreen forest.

i. Sal forest:

  • Sal (Shorea robusta), is an extremely gregarious species. It is dominant throughout the Indo-Gangetic plain and sub-Himalayan tracts.
  • It sometimes grows upto 1,500m on the outer foothills which constitute the predominant Hill or Montane Sal forest. The trees are luxuriant growing up from 25 to 45m in height in Terai and Dun valleys but in the hills these grow upto 15m.
  • Sal forest has greatly suffered from lopping and falling of trees by local inhabitants in eastern and central Nepal while it forms some magnificent stands of tall trees in the western Nepal.
  • The common tree associates are Terminalia belliraca, T. chebula, Dillenia pentagyna, Butea monosperma, Mimosarubbicaulis, M. pudica.

ii. Tropical deciduous riverine forest:

  • It is found along the streams of Bhabar and Dun valleys.
  • Khair (Acacia catechu) and Sisso (Dalbergia sissoo) are predominant at water’s edges with undergrowth of Pogostemon benghalensis, Justicia adhatoda,etc.
  • On the riverside terraces Bombax ceiba becomes dominant with Toona ciliate, Sygium cumini, Ehretia laevis.
  • Along the riversidein the open areas, Saccharum bengalense and S. spontaneoum and Arundo donax grow densely.

 iii. Tropical evergreen forest:

  • This type of forest is confined to the humid north-facing slopes of tropical zone in the outer foothills of east Nepal.
  • Michelia champaca is predominantly associated with laurels such as Litsea polyantha, L. doshia, Persea duthei. Other commonly associated species is Murraya paniculate, Calamus acanthospathus.

SUBTROPICAL ZONE:

  • This zone prevails to an elevation of 1,000-2,000m.
  • It comprises the outer foothills, lower parts of Mahabharat range, midland areas and Himalayas.
  • Schima- Castanopsis, Pinus roxburghii and Alnus nepalensis are the important forest types.

i. Schima-Castanopsis Forest:

  • Chilaune (Schima wallichii) and Katush (Castanopsis indica) type of forest is dominant between 1,000-1,700m on both the north and south-facing slopes in east and central Nepal.
  • Most of the natural forest in this zone are cleared for cultivation purpose.
  • At its upper limit above 1,700m Castanopsis tribuloides is dominant which occasionally forms pure Katush forest with C. hystrix in East Nepal.
  • The associated tree species are Engelhardia spicata, Acer oblungum, Michelia kisopa, Persea odoratissimia, Litsea doshia, Ficus nerrifolius, F. auriculate, etc.

ii. Pine forest:

  • Pinus roxburghii (Chir pine) is dominant in between 900-2,000m on both the south and north facing slopes in west Nepal.
  • This type of forest is largely confined to the dry situations in central Nepal.
  • The top canopy is composed exclusively of chir pine, with straight unbranched trunks.
  • The ground layer is poorly represented by a limited number of species as Wendlandia puberula, Inula cappa, Woodfordia fruticose, Anaphalis busua, etc.
  • In the damp gullies in west Nepal it is associated with Oak forest.
  • In east Nepal it is very scarce and occurs in limited amounts in the lower part of the Arun and Tamur valleys.

iii. Alder forest:

  • The common alder in Nepal is Alnus nepalensis, locally known as Utis.
  • It occurs most prominently in the form of small isolated woods along the banks of streams and field margins, and on unstable ground which is unsuitable for cultivation.
  • Most of the subtropical and temperate zones (900-2700m) in central and east Nepal, the alder often grows in places in the Schima-Castanopsis forest or penetrates to the upper temperate mixed broad-leaved forest upto 2700m.
  • In west Nepal, alder occurs with oak forest and in Aesculus-Juglans-Acer forest.
  • The undergrowth plants are very limited and include Rosa brunonii, Coriaria nepalensis, Princepia utilis etc.

TEMPERATE ZONE:

  • It runs almost parallel and north to outer foothills from east to west and includes mainly the Mahabharat range and the southern sides of the main Himalayan ranges.
  • The region falls at an altitude of 2,000-3,000 m and is characterized by lower temperate mixed broad-leaved forest, temperate mixed evergreen forest, and upper temperate mixed broad-leaved forest.

i. Lower temperature mixed broad-leaved forest:

  • It is usually limited on the north and west facing slopes between 1,700-2,200m in small patches in damp places throughout the midlands.
  • It is more prominent on the upper Arun and Tamur valleys in east Nepal and the south of Annapurna and Himalchuli ranges in central Nepal.
  • The forest is evergreen majorly composed of laurels such as Persia duthiei, P. odoratissima, P. pallida, Neolitsea pallens etc.

ii. Temperate mixed evergreen forest:

  • It is mainly composed mainly of Broad-leaved oak and Conifers between 2,100-2,700m.
  • Broad-leaved oak forest is more common in east and central Nepal and are dominant on the slopes which face north and west.
  • The important species are Quercus lamellose, Q. glauca, Q. semecarpifolia etc.
  • This type of forest is heavily destroyed by villagers for fodder and fuelwood.
  • Conifer forests are more numerous in west Nepal and are dominated by western elements such as Picea smithiana, Abies pindrow, Cupressus torulosa, Cedrus deodara.
  • Between 2,200m-3,200m in Humla-Jumla areas, Pinus wallichiana forms extensive pure forest on south facing slopes while Picea smithiana are confined mostly to north facing or west facing slopes in less distributed localities. However, such forests are scarce in the east Nepal.
  • Broad-leaved Oak and Conifer type of forests are associated with Lyonia ovalifolia, Betula alnoides, Rhus wallichii, Hedera nepalensis etc, a beautiful ground orchid is occasionally seen on the grassy slopes.

iii. Upper temperate mixed broad-leaved forest:

  • It is mainly composed of deciduous trees and is widespread between 2,400-3,000m in the north facing and west facing slopes.
  • Aesculus-Juglans-Acer association is quite widespread in west Nepal. This consists of Asculus indica, Juglans regia, Acer caesium etc with a number of western elements such as Corylus jacquemontii, Syringa emodi, Ulmus wallichiana, Morus serrata, etc.
  • This zone is replaced by Magnolia-Acer-Osmanthus association in the east and the central Nepal. Magnolia campbellii, Acer campbellii, Osmathus suavis, Corylus ferox etc are the common species.
  • The associated plants are Sorbus cuspidata, Ilex dipyrena, Pieris Formosa, Gaultheria hookeri, G. griffithiana, Holboellia latifolia, Schisandra grandiflora, and several species of Rhododendron (R. hodgsonii, R. falconeri, and R. arboretum – national flower of Nepal    -The common associated herbs in temperate zone include Luculia   gratissimia, Lilium wallichianum, Piptanthus nepalensis, Aster himalaicus, etc.

SUBALPINE ZONE:

  • It covers the part of the greater Himalayas between 3,000-4,100m.
  • It is characterized by Silver fir and Birch-Rhododendron forests.

i. Silver Fir forest:

  • Silver fir (Abies spectabilis) forest is predominant between 2,900m and the treeline (3,850m).
  • The treeline is estimated to be approx. 4,000 m in eastern Nepal, while it goes down decreasing to approx. 3,800 m and 3,650 m in central and western Nepal respectively.
  • The upper canopy of the forest is composed exclusively of silver fir tree attaining normally a height of 25-32 m.
  • A continuous belt of this forest is found in central Nepal between 2,900-3,800m on the south-facing slopes.
  • The fir forest normally had a dense understorey of Rhododendrons (R. barbatum, R. campanulatum) which represents one of the most beautiful sights in Nepal.
  • In the extreme east Larix griffithiana and in the Langtang area of central midland L. himalaica occur associated with silver fir and maple (Acer spp.) forests.
  • Pure fir forest is also much less extensive in the west midlands. It is often broken up by the stands of Quercus semecarpifolia which reaches upto the treeline.

ii. Birch-Rhododendron forest:

  • Betula utilis (birch), locally known as Bhoj patra is widespread in Nepal.
  • It usually occurs between 3,300-3,800m and in many places forms a pure belt.
  • The upper storey of birch forest is composed either exclusively of birch or with constant association of Rhododendron campanulatum.
  • The trees rarely exceed 10m in height, and their twisted stems are often covered with peeling stripes of pink papery smooth bark.
  • In the areas of heavy rainfall in east Nepal, the birch in places appears to be unable to compete with the dense growth of Rhododendron spp. (R. barbatum, R. cowanianum, R. falconeri, etc.)
  • In the west region, the birch occurs mixed with fir and oak. In the inner valleys it occurs with Juniperus recurve, Prunus cornuta, and shrubs, climbers and herbs are Lonicera myrtillus, Cortoneaster acuminatus, Campanula latifolia, Inula roylena, Rhodiola himalensis etc.

ALPINE ZONE:

  • This zone above 4,100m comprises the association of Juniper-Rhododendron-Caragana- Lonicera, and alpine meadows.

i. Juniper-Rhododendron meadows

  • In the heads of Inner valleys between 4,000-4,300m, Juniper-Rhododendron association includes Juniperus spp (J. recurva, J. indica, J. indica) and Rhododendron spp. (R. anthopogon, R. lepidotum) on exposed slopes.
  • The other associated species are Lonicera myrtillus, L. obovata, Ephedra gerardiana, Spiraea arcuate, etc.
  • Some of the striking and ornamental plants in this belt are Anemone obtusiloba, Campanula aristate, Corydalis meifolia, C. ramosa, Delphinium brunonianum, D. vestitum, Gentiana depressa, G. prolata, G. venusta, Maharanga emodi, Mecanopsis dhwojii, M. horridula, M. simplicifolia, Primula calderana, P. sikkimensis, P. tibetica etc.

ii. Caragana-Lonicera meadows

  • In the arid region to the north of the Dhaulagiri-Annapurna massif, the climate and flora are very much like those in the Tibetan plateau.
  • Caragana versicolor and Lonicera spinosa dominate at 4,100-4,800m and are associated with Rosa sericea, Potentilla fructicosa, Myricaria rosea, Caragana brevispina, Sophora moorcroftiana, etc.

iii. Alpine meadows:

  • Meadows at high altitude locally called Kharka, are subjected to grazing in summer and rainy seasons.
  • They are comprised mainly of Kobresia seliculmus and K. trivenis.
  • The other subsidiary species are Agrostis munroana, Carex atrofusca, C. microglochin, Caltha palustris, etc.
  • Above 4,800m plant association diminishes and appears scattered on the exposed rocky screes and stony slopes.
  • Some of these are Primula minutissima, P. walshii, Androsace lehmannii, A. tapete, A. muscoidea, Potentilla biflora, Saussurea simponiana, S. tridactyle, S. gossypiphora, etc.

REFERENCES:

  1. https://www.manang.com/nepal/general_information_about_nepal/flora_fauna_of_nepal.php
  2. http://www.fao.org/3/ae154e/AE154E04.htm
  3. https://www.kullabs.com/classes/subjects/units/lessons/notes/note-detail/233
  4. Chaudhary Ram P., M.Sc., Ph.D., D.Sc., F.N.R.S., Professor of Botany, TU, Kirtipur, Ktm, Nepal, Biodiversity in Nepal,1998.

Types of Forest in Nepal