(Last Updated on : 21-10-2013)
Several forest types are included in the Himalayan Subtropical Broadleaf Forests ecoregion in India. The forest types include the Dodonea scrub, the subtropical dry evergreen forests of Olea cuspidata, the northern dry mixed deciduous forests, the dry Siwalik sal (Shorea robusta) forests, the moist mixed deciduous forests, the northern tropical semi-evergreen forests, and the northern tropical wet evergreen forests. However, among all these, the Himalayan subtropical broadleaf forests in India are noteworthy for their rich diversity of flora and fauna species.
The east-west-directed Himalayan subtropical broadleaf forests in India are located along the Siwaliks or Outer Himalayan Range and lie between 500 and 1,000 m. Though the forests achieve their greatest coverage in the middle hills of central Nepal, a part of them extends through Darjeeling into Bhutan and also into the Indian State of Uttar Pradesh. The eco-region is being bisected by the Kali Gandaki River that has gouged the world's deepest river valley through the Himalayan Range. The region also forms a critical link in the chain of interconnected Himalayan ecosystems that extend from the Terai and Duar grasslands along the foothills to the high alpine meadows at the top of the world's highest mountain range.
The Himalayan subtropical broadleaf forests in India are composed of alluvium deposited over the ages by the rivers that drain this young mountain range. The annual rainfall in the forests varies from east to west; however, it can reach up to 2,000 m. The forests capture moisture from the monsoons that sweep in from the Bay of Bengal, and most of this rainfall is expended in the eastern Himalayas. The Himalayan subtropical broadleaf forests in India have quite a rich biodiversity. The average height of the trees in these forests is 30 m; however, the canopy can reach as high as 50 m, in favourable areas. Compared to the tropical evergreen forests, the top canopy of these forests is less dense and the mid-canopy and shrubby undergrowth are easily recognisable. Though, there are no grasses, the forests have a well-developed herb cover. The climbers and epiphytes are quite common in these forests.
The diversity and richness of woody species in the Himalayan subtropical broadleaf forests in India generally decrease from east to west. The characteristic tree communities in the western foothills of Himachal Pradesh and Uttar Pradesh are represented by Shorea robusta, Terminalia tomentosa, Anogeissus latifolia, Mallotus philippinensis, Olea cuspidata, Bauhinia restusa, and Bauhinia variegata etc. On the other hand, the characteristic species in the eastern foothills include Schima wallichii, Castanopsis tribuloides, C. indica, Terminalia crenulata, Terminalia bellerica, Engelhardtia spicata, Betula spp., and Anogeissus spp. etc. The entire eco-region is acting as a critical link in the Himalayan ecosystem, where the altitudinal connectivity between the habitat types is important for ecosystem function. Apart from maintaining ecosystem dynamics, the region is also harbouring several threatened species that warrant conservation attention.
The Himalayan subtropical broadleaf forests in India are home to numerous species of mammal fauna. The forests comprise ninety-seven species of mammal fauna, out of which one species is endemic to this region. The endemic and near-endemic mammal species in these forests include the Semnopithecus geei, under the Cercopithecidae family. This golden langur has a small range distribution and is limited to the broadleaf forests north of the Brahmaputra River. Apart from this, there are also several other mammal species found in these forests that are considered as threatened. These species include the Tiger, Asian Elephant, Golden Langur, Smooth-Coated Otter, Clouded Leopard, Gaur, Serow, Irrawaddy Squirrel, and Parti-coloured Squirrel, etc. The bird fauna in the forests is also quite rich, consisting of more than 340 bird species. Among these, one species is endemic to the ecoregion. This endemic and near-endemic bird species is the Chestnut-breasted partridge under the Phasianidae family. Apart from this, the globally recognised threatened species like the White-Winged Wood Duck and five Hornbill species are also found in the Himalayan subtropical broadleaf forests in India.