Nepal is a land of geographical extremes, ranging from near sea level elevations in the southern Terai to the world's highest mountains. The country contains a variety of ecosystems; treeless sub alpine pastures and dense fir forests of the high valleys, oak and rhododendron woods of the middle hills, and tall sal forests of the south. Along the southern borders of Nepal are preserved much of the lowland jungles and grasslands that once covered this part of the sub continent.
Ranging from the subtropical forests of the Terai to the great peaks of the Himalayas in the north, Nepal abounds with some of the most spectacular sceneries in the whole of Asia, with a variety of fauna and flora also unparalleled elsewhere in the region. Between Nepal's geographical extremes, one may find every vegetation type, from the treeless steppes of the Trans-Himalayan region in the extreme north and the birch, silver fir, larch and hemlock of the higher valleys to the oak, pine and rhododendron of the intermediate altitudes and the great sal and sissau forests of the south.
Dominant in the Langtang Valley are the chir pine, willow, alder, and evergreen oak. Blue pine and silver fir are frequent in the subalpine zone, which also supports tree rhododendrons— magnificent plants often reaching a growth of 12 m (40 ft). Ground orchids, lilies, yellow and blue poppies, and crimson anemones are prevalent in central Nepal. The profusion of wild flowers extends to very high altitudes; at 5,200 m (17,000 ft), several varieties of primula, pink and white cotoneaster, and white erica have been gathered, along with many kinds of alpine mosses and ferns.
Nepal's flora and fauna can be divided into four regions:-
Tropical Deciduous Monsoon Forest:
This includes the Terai plains and the broad flat valleys or Duns found between hill ranges. The dominant tree species of this area are Sal (Shorea robusta), sometimes associated with Semal (Bombax malabricum), Asna (Terminalia termentosa), Dalbergia spp. and other species, and Pinus roxburghi occuring on the higher ridges of the Churia hills, which in places reach an altitude of 1,800 meters.
Subtropical Mixed Evergreen Forest:
This includes the Mahabharat Lekh which rises to a height of about 2,400 meters and comprises the outer wall of the Himalayan range. Great rivers such as the Karnali, Narayani, and Sapta Koshi flow through this area into the plains of the Terai. This zone also includes the so called "middle hills", which extend northward in a somewhat confused maze of ridges and valleys to the foot of the great Himalaya.
Temperate Evergreen Forest:
Northward on the lower slopes and spurs of the Great Himalaya, oaks and pines are the dominant species up to an altitude of about 2,400 meters Above these are found dense conifer forest of Picea, Tsuga, Larix and Betula spp. Abies and Betula are usually confined to higher elevations, with Betula typically marking the upper limit of the tree line. At about 3,600 to 3,900 meters rhododendron, bamboo and maples commonly mingle with the conifers. The composition of the forest varies considerably, with coniferous predominating in the west and eracaceous in the east.
Sub alpine and Alpine Zone:
Above the tree line, rhododendron, juniper scrub and other procumbent woody vegetation may extend to about 4,200 meters where they are then succeeded by a tundra?like association of short grasses, sedge mosses and alpine plants wherever there is sufficient soil. This continues up to the lower limit of perpetual snow and ice at about 5,100 meters. The mammalian fauna is sparse and unlikely to include any species other than the Himalayan marmot, mouse hare, tahr, musk deer, snow leopard and occasionally blue sheep. In former times, the wild yak and great Tibetan sheep could also be sighted in this region and it is possible that a few may still be surviving in areas such as Dolpa and Humla.
