|Copyright: Subhash Ranjan (sranjan)
|Date Taken: 2008-10-22|
|Camera: Olympus Sp 510uz|
|Photo Version: Original Version|
|Date Submitted: 2009-05-07 4:53|
|[Note Guidelines] Photographer's Note|
|Unique epiphytic mosses were seen on the conifers....altitude 12,000 feet above sea level.|
Biodiversity of Sikkim's Four Eco Regions
Sikkim is a land of vast variation in altitude within very short distances ranging from around 300m to 8585m. Elevation plays a prime role in fashioning the eco-regions of the state. This is evident from the presence of Sal forests in the Rangeet Valley in the south to the temperate fir forests in the north, beyond which lie the trans-Himalayas and cold desert of the Tibetan plateau. Broadly speaking there are four zones of vegetation according to altitude variations, but in some stray areas, altitude alone may not define a zone as exposure to other physical properties of the terrain can result otherwise.
This zone lies between the 300 m. low river valleys to the mid-hill heights of around 1200 m. The topographical features are deep valleys and gorges with well-drained slopes. Beneath canopies of tall evergreen and semi-deciduous trees, the dense undergrowth in this belt includes various species of orchids, Rhapidophora, wild banana, Pandanus, nettles and giant bamboo. The Rangeet Valley area has an abundance of sal forests (Shorea robusta), a magnificent timber tree remarkable for its robustness and longevity.
This region has a range from about 1800 m to 3000 m and the physical features associated with this belt are the upper portions of high hills. Rainfall is heaviest in this zone and conditions remain humid throughout the year.
The vegetation in the upper storey consists mainly of Castanopsis hystrix (chestnut), Machilus spp. (Kawla), Rhododendron spp. (Chimal), Symplocos spicata (Kholme), Symplocos theifolia (Kharane), Michelia excelsa (magnolia), Quercus lamellosa (Himalayan Oak), Quercus lineata (Phalant), Leucoseptrum canum (Ghurpis), Quercus pachyphylla (Sungure Katus), Betula alnoides (Saur), Nyssa javanica (Lekh Chilaune), Bucklandia populnea (Pipli). In the underwood, Engelhardtia spicata (Mahuwa), Eurya japonica (Jhingni), Rhododendron arboreum (Gurans) and Viburnum spp. (Asare), are the predominant species.
In the upper reaches, dense tall evergreen forests with oak and rhododendron predominate. The upper storey consists of Quercus lamellosa (Himalayan Oak), Q. lineata (Phalant), Machilus spp. (Kaula). The undergrowth consists of Arundinaria maling (dwarf bamboo), dwarf rhododendron, ferns, epiphytic moss and orchids.
Plantations of Large Cardamom beneath canopies of tall trees in forest patches, terraced farmland, and a tea estate at Temi are the dominant features of the landscape as much as the well matured exotic Cryptomeria japonica trees that were introduced to the region around a century back.
Temperate & Alpine
The region extends from 3000m to 4000m with mixed coniferous forests of hemlock, spruce, pine, fir and juniper with shrubby undergrowth of Rhododendron and dwarf bamboo. Seabuckthorn, Hippophae spp. occurs in the wild; some of which is collected for medicinal purposes and also for its use as a dye.
The Alpine forests and scrub extend up to 4,500 m with small crooked trees and large shrubs interspersed with fir and pine. The stunted forest is mainly of rhododendron of many species.
Several plants found in this region attract interest for use in traditional medicine. Dwarf rhododendron leaves are used for burning as incense. This region has a very small resident human population, mainly Bhutias and mostly pastoral, herding livestock such as yaks and dairy cattle.
This region lies between 4500 m and 5500m and is characterized by cold desert vegetation, a feature exclusively restricted to the north of Sikkim. This eco-region has not yet been included in the protected area network of the state and is perhaps the most threatened as it contains a host of endangered species. The region has a short four-month growing season during which grass, flowering plants and herbs grow abundantly supporting a host of insect fauna as well as wild and domestic herbivores, larks and finches.
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