Included here are the Himalayas which in biogeographic terms can be divided into the western and eastern Himalayas. The western zone includes the area westward of the Kali Gandaki River Gorge (the world’s deepest valley) in Central Nepal which acts as a biogeographic barrier between the Eastern and Western Himalayan. Also included are the southern slopes and offspurs of the Western Himalayas, the valleys of the rivers Gilgat, Kabul, Kunar, Kurram and Swat, and with mountains like Everest, Dhaulagiri and Makalu, this zone has the tallest peaks on Earth. The eastern Himalayas includes eastern Nepal, Darjeeling, Sikkim, Bhutan, a large part of the Assam Himalayas and the extreme southeastern part of Tibet.

Eastern Himalayan Broadleaf Forest

These temperate forests range in altitude from about 1500 m and 3000 m and stretch from the deep Kali Gandaki River Gorge in central Nepal though Bhutan and into India’s eastern state of Arunachal Pradesh. Up to about 1500m, mixed forests occur characterized by Castanopsis indica, Engelhardtia spicata and Schima wallichii. Endemic species found in this general zone include Argyreia hookeri (Convolvulaceae), Begonia rubella (Begoniaceae), Entata phaseoloides (family?), Orthosiphon incurvus (Lamiaceae), Pandanus nepalensis (Pandanaceae), Rhaphidophora glauca (Araceae), Thomsonia nepalensis (Araceae) and the epiphytic orchids Bulbophyllum affine, Coelogyne flaccida Cryoptochilus luteus (Orchidaceae). Above 1500m and extending up to about 2700m, the forests are predominantly composed of evergreen oak. These are dominated by species such as Quercus fenestrata, Q. lamellosa, Q. pachyphylla, Q. spicata, Lithocarpus pachyphylla, Rododendron arborea, Schima wallichii, Symingtonia populnea, and include the endemic rhododendrons, Rhododendron falconeri, R. thomsonii and R. virgatum (Ericaceae).  Other endemics include Buddleja conilei (Scrophulariaceae) and the climbers Aristolochia griffithii (Aristolochiaceae) and Porana grandiflorum (Convolvulaceae) in the scrub layer, while in the ground layer include Arisaema griffithii, A. erubescens (Araceae), Impatiens stenantha (Balsaminaceae), Viola wallichiana (Violaceae) and the orchids Calanthe brevicorum and Vandopsis undulata (Orchidaceae). In places however the endemic grass Arundinaria maling (Poaceae) may form dense thickets in the undergrowth. Finally, the many epiphytes of these forests include endemics such as Aeschynanthus sikkimensis (Gesneriaceae), Agapetes serpens, A. incurvatus (Ericaceae), and Cymbidium longifolium (Orchidaceae).

Eastern Himalayan Subalpine Conifer and Rhododendron Forests

At heights above 2700 m a mixture of conifers and rhododendrons dominate the forests. Up to about 2900 m the near endemic Tsuga dumosa (Pinaceae) is the main conifer, but at higher elevations this gives way to the endemic Abies spectabilis (A. densa) (Pinaceae). Other endemic or near endemic conifers include Larex griffithiana, L. himalaica (Pinaceae) and Pinus willichiana (Pinaceae). The main rhododendron species include endemics such as Rhododendron grande, R. hodgsonii, R. wightii and R. setosum (Ericaceae),with the latter species becoming dominant in the upper limits of forest at about 4000 m.  Other endemic rhododendrons found include R. cowanianum and the epiphytic R. camelliflorum and R. pendulum. The herbaceous flora is not as rich as at lower elevations but nevertheless includes a number of endemics such as Aconitum spicatum (Ranunculaceae), Cypripedium elegans (Orchidaceae), Impatiens falcifer (Balsaminaceae), Primula gracilipes (Primulaceae)and Rodgersia nepalensis (Saxifragaceae), while in forest clearing the spectacular endemic umbillifer Angelica cyclocarpa (Apiaceae) can be found growing up to 3 m tall.  However, there are a number of variations in forest type. On top of Bhandukay Bhajanj, for example, at a height of about 3100 m there is a forest dominated by the near endemic Daphniphyllum himalayense (Daphniphyllaceae) associated with Rhododendron arboreum var. campbelliae, R. barbatum and R. grande. It is here that the strange vesseless dicotyledon Tetracentron sinense var. himalense was discovered - a species that has been placed in its own family (Tetracentraceae) and appears to have features in common with the primitive family Winteraceae.

Western Himalayan Broadleaf Forest

Forming a band between altitudes of 1500 m and 2600 m these rich temperate forests extend along much of the southern slopes of the Western Himalayas. As with the Eastern Himalayas, these include both evergreen and deciduous forest.  The former is dominated by Quercus dilatata, Q. incana, Q. lamellosa and Q. semecarpifolia, and often includes a variety of lauraceous species such as Litsea lanugunosa, L. umbrosa, Machilus odoratissima and Phoebe pulcherrima. The under story is often rich in mosses and ferns, while the trees provide habitat for a rich variety of epiphytes, especially orchids, ferns and aroids.  Endemic trees in this zone include Acer acuminatum (Aceraceae), Carpinus faginea (Betulaceae), Fraxinus micrantha (Oleaceae) and the palm Trachycarpus takil (Arecaceae). In fact, this is one of the few palm species in the world that can grow at high altitude. Other endemic forest dwellers include Caragana brevispina (Fabiaceae), Primula edgeworthii, P. sessilis (Primulaceae), and Pteracanthus urticifolius (Acanthaceae).  The deciduous forests tend to be distributed along riverbanks and include species such as Carpinus viminea, Juglans regia the endemic Aesculus indica (Sapindaceae) and near endemic Alnus nepalensis (Betulaceae). However, at high altitudes along the upper Karnali River, the latter species is replaced by the endemic Alnus nitida (Betulaceae). 

Western Himalayan Subalpine Conifer Forest

Roughly between altitudes of 2400-3500 m these extensive conifer forests stretch from central Nepal in the east to Jamma, Kashmir and beyond the Pakistan border in the west. The dominant tree species include Abies sectabilis, A. pindrow the endemic Picea smithiana (Pinaceae) and near endemic Pinus gerardiana (Pinaceae). However, they show several recognizable variations, with oak and rhododendron forming conspicuous components in some areas, while in some of the dryer areas above 2400 m, forests of the endemic Cedrus deodora occurs. These deodora forests provided habitat for several other endemic species including Cupressus torulosa (Cupressaceae), Pseudomertensia racemosa (Boraginaceae) and Rhododendron lowndesii (Ericaceae), although the former species seems to be confined to limestone areas. Other endemics generally confined to these subalpine conifer forests include Iris milesii (Iridaceae) and the orchid Elophia dabia (Orchidaceae).

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