The topographic, climatic and edaphic diversity of Nepal has greatly affected the diversity of plants. So several types of forests are found here. The Forest of Nepal is categorized into the following types according to altitudinal variation. (Stainton 1974 A.D.)
1. Tropical forest
It is extended from east to west below the altitude of 1000m. It is subdivided into the following types:
a. Sal forest: dominant species is Sal (Shorea robusta) sometimes extends up to 1500m of lower hills. Other species are Terminalia chebula (harro), T. bellirica (barro), Syzygium cumuni (jamun), Bauhinia vahlii (borio), Cassia tora (tapre), Cyperus difformis (mothe), Lagerstroemia parviflora (dhayari), etc.
b.Tropical deciduous riverine forest: It is found along the streams of Bhavar and Dun valleys. The major vegetations found in this forest are Justicia adhatoda (asuro), Colebrookea oppositifolia (dhursil), Syzygium cumini (jamun), Toona ciliata (tooni), etc. In the open area along the riverside, several grass species are found. These Saccharum bengalensis (elephant grass), S. spontaneum (kans), Imperata cylindrica (siru), etc.
c. Tropical evergreen forest: in humid north-facing slopes of terai. Michelia champaca (champ) is dominant and other plants are Litsea monopetala (kutmiro), Murraya panicula (kamani), Calamus acanthospathus (bet), Cycas pectinata (thakal), etc. These plants remain evergreen throughout the year.
2. Subtropical forest:
It is found from 1000-2000m of altitude. It is subdivided into the following types.
a.Schima- Castanopsis forest: This forest is extended from 1000-1700m of altitude. Schima wallichii (chilaune) and Castanopsis indica (katus) are dominant species in this type of forest. Castanopsis tribuloides (musure katus), Michelia kisopa (ban champ), Ficus nerifolia (dudhilo) Rhus parviflora (amaro), Eupatorium adenophorum (banmara), etc. are also found.
b.Pine forest: Pinus roxburghii (rani salla) is dominant in this forest from 900-2000m of altitude. It is found in both north and south-facing slopes. The ground layer of this forest is covered by Woodfordia fruticosa (sano dhayari), Anaphalis busua (seto ekle ghans), Inula capa (gai tihare), etc. In some regions associated with oak forest consisting of different species Quercus (oak-banjh/phalant).
c.Alder forest: extended from 900-2700m of altitude. The dominant species of this forest is Alnus nepalensis (utis). It is commonly found in banks of streams, field margins and unstable land, which is unsuitable for cultivation.
3. Temperate forest
This forest is found from 2000-3000m of altitude, subdivided into the following types:
a. Lower temperate mixed broad-leaved forest: It is mainly found on north and west-facing slopes between 1700-2200m of altitude in small patches in the damp places in the midlands. This forest consists of Persea gamblei (kaulo), Cinnamomum tamala (tej pat), C. zeylanicum (dalchini), Litsea monopetala (kutmiro), etc.
b.Temperate mixed evergreen forest: This forest consists of broad-leaved and conifers between 2100-2700m of altitude. Some places in this forest are rich in broad-leaved vegetations like oaks include Quercus lanata (banjh), Q. glauca (phalant), Q. semicarpifolia (khasra), Lithocarpus pachyphylla (thulo katus), etc. In some places, conifers like Abies pindrow (thing sallo), Cupressus torulosa (raj sallo), Cedrus deodara (deodar), Pinus wallichiana (gobre salla) are dominantly found. Both conifers and broad-leaved plants mixed in some regions.
c.Upper temperate mixed broad-leaved forest: spread from 2400- 3000m of altitude and composed of deciduous trees. It consists of Juglans regia (okhar), Aesculus indica (pangro), Acer oblongum (firfire), etc. Several species of Rhododendron (gurans) are also found in this forest.
4. Subalpine forest:
It extends from 3000-4100m of altitude. It is subdivided into the following types:
a.Silver fir forest: Abies spectabilis (talis patra) is the dominant species of this forest and extended between 2900-3850m of altitude. It is mostly found in the south-facing slopes of the central Langtang region, Larix himalaica (lekh sallo) is found. In some regions, this forest is interrupted by the Quercus forest.
b.Birch-Rhododendron forest: It is found between 3300-3800m of altitude. This forest consists of Betula utilis (bhoj patra) and Rhododendron (gurans). In the eastern region, dense growth of species has been found. These include R. barbatum, R. campanulatum, R. cowanianum, R. falconeri, R. hodgsonii, etc.
It is extended from 4100-above. Large trees not found. It consists following types of vegetation:
a.Juniper-Rhododendron forest: found in the inner valleys from 4000- 4300m of altitude.Several species of Juniperus (dhupi), eg: J. recurva, J. indica, J. communis associated with Rhododendron (R. anthopogon, R. lepidotum). Ephedra gerardiana (somlata) Lonicera species (kanike) are also associated with this forest.
b.Caragana-Lonicera forest: It extended from 4100-4800m of altitude and mostly north of the Dhaulagiri- Annapurna range.It consists of Lonicera spinosa and Caragana venicolor (sherma).
c.Alpine meadows: These are high-altitude grasslands (kharks). They are subjected to grazing in the rainy season. During winter, they are covered by snow. Only grasses are found in such regions. The major vegetations in this area are Primula minutissima (medosero), P walshil, Potentilla fulgens (bajra danti), Saxifraga stenophylla, etc. Above 4800m, the vegetations are limited only in the form of moss.