The Eastern Himalayan Sub-Alpine Conifer Forests represent the transition from the forested ecoregions of the Himalayas to treeless alpine meadows and boulder-strewn alpine screes. Their ecological role within the interconnected Himalayan ecosystem, which extends from the alluvial grasslands along the foothills to the high alpine meadows, makes the forests of this ecoregion a conservation priority. Conservation of the Himalayan biodiversity is contingent on protecting the interconnected processes among the Himalayan ecosystems. For instance, several Himalayan birds and mammals exhibit altitudinal seasonal migrations and depend on contiguous habitats that permit these movements. The integrity of the watersheds of the rivers that originate in the high mountains of this majestic range depends on the intactness of habitat, from the high elevations to the lowlands. If any of the habitat layers are lost or degraded, these processes will also be disrupted.
The ecoregion straddles the transition from the southern Indo-Malayan to the northern Palearctic fauna. Here tigers yield to snow leopards, and sambar are replaced by blue sheep. But the ecoregion also has its own specialized flora and fauna, such as the musk deer and red panda, which are limited to these mature temperate conifer forests.
Location and General Description
The ecoregion represents the belt of conifer forest between 3,000 and 4,000 meters, from east of the Kali Gandaki River in Nepal through Bhutan and into the state of Arunachal Pradesh, in India. These forests usually are confined to the steeper, rocky, north-facing slopes and therefore are inaccessible to human habitation and cultivation.
The ecoregion has recent origins. The Himalayas were born of the tumultuous collision between the northward-drifting Deccan Plate and the Eurasian continent during the Cretaceous. The Himalayas were created during this and three subsequent periods of geologic upheaval and uplift.
Today, the Himalayan Mountain Range comprises three east-west-directed parallel zones. The southernmost is the outer Himalayas, also known as the Siwaliks, which lies adjacent to the Indo-Gangetic Plain. The Middle Himalayas represent a series of ridges and valleys that rise to about 5,000 meters and contain this ecoregion. The Inner Himalayas are where the imposing, giant peaks such as Everest, Makalu, and Dhaulagiri tower far above the Deccan Plateau.
The Himalayas capture moisture from the monsoons that sweep in from the Bay of Bengal. Therefore, the eastern Himalayas, being closer to the source, receive more precipitation than the western Himalayas. This trend is reflected in the timberline, which declines from 4,500 meters in the east to about 3,600 meters in the west.
These temperate conifer forests are dominated by fir (Abies spectabilis), larch (Larix griffithii), hemlock (Tsuga dumosa), Juniperus recurva, and Juniperus indica. Several colorful rhododendrons (Rhododendron hodgsonii, R. barbatum, R. campylocarpum, R. campanulatum, R. fulgens, R. thomsonii) grow profusely in the understory, along with Viburnum grandiflorum, Lonicera angustifolia, Betula utilis, Acer spp., Sorbus spp., Juniperus indica, and J. recurva. There is considerable species turnover among the rhododendrons along the east-west axis. Species common in central Nepal can be absent from the community in eastern Bhutan. This contributes to the overall diversity of the ecoregion.
Between 2,500 and 3,000 meters, the wetter areas are dominated by Tsuga dumosa, which also forms mixed stands with fir. Blue pine (Pinus wallichiana) occurs in the drier inner valleys closer to Tibet. Blue pine is especially common in the Khumbu region, where it forms a distinct community. Patches of pure birch (Betula utilis) represent a pioneer stage that climaxes as a Betula-Abies mixed forest. Taxus baccata is an important, uncommon species in this forest community.
Juniper woodland is another distinct habitat type within this sub-alpine conifer zone. It characteristically grows along the flat, inner river valleys with willow (Salix spp.) and Prunus spp. The juniper woodlands in Tsarijathang, in Jigme Dorji National Park, Bhutan, in particular are used by takin (Budorcas taxicolor) as summer habitat.
Overall, the mammal fauna consists of eighty-nine species. The ecoregion lies within the ecotone between the Indo-Malayan and Palearctic zoogeographic zones. Therefore, the mammal fauna from both zones, such as civets, martens, Himalayan tahr, and muntjac are included within the ecoregion. Three species-two squirrels and a murid rodent-with limited distributions are considered to be endemic to the ecoregion (Table 1). Whereas the squirrels are near-endemic species that are shared with neighboring ecoregions, Apodemus gurkha is a strict endemic that has been recorded only from this ecoregion.
|Table 1. Endemic and Near-Endemic Mammal Species.|
|An asterisk signifies that the species' range is limited to this ecoregion.|
Although not endemic species, the red panda and the Himalayan musk deer (Moschus chrysogaster) are characteristic of the mature fir forests represented by this ecoregion. The red pandas usually are limited to Abies-ringal bamboo forests between 3,000 and 4,000 meters, where precipitation is high. The musk deer is widely hunted for its musk glands, which allegedly have pharmaceutical properties. The waxy, brown musk (a single musk gland yields about 25 grams of musk) can fetch as much as US$45,000 per kilogram on the international market.
The ecoregion harbors several threatened species, including the endangered red panda (Ailurus fulgens), takin (Budorcas taxicolor), serow (Capricornis sumatraensis), and particolored squirrel (Hylopetes alboniger). The endangered tiger (Panthera tigris) roams the broadleaf forests lower down and occasionally ventures into these conifer forests. But the prey base in the conifer forests is insufficient to harbor a viable resident population within this ecoregion. In addition to these endangered species, the following species are considered vulnerable and should also receive conservation attention: the Vespertilionidae bat Myotis sicarius, wild dog (Cuon alpinus), Asiatic black bear (Ursus thibetanus), and Himalayan tahr (Hemitragus jemlahicus).
There are more than 200 species of birds known to this ecoregion, of which six are considered endemic to the ecoregion (Table 2).
|Table 2. Endemic and Near-Endemic Bird Species.|
|Phasianidae||Chestnut-breasted partridge||Arborophila mandellii|
|Phasianidae||Buff-throated partridge||Tetraophasis szechenyii*|
|Timaliidae||Hoary-throated barwing||Actinodura nipalensis|
|Timaliidae||Ludlow's fulvetta||Alcippe ludlowi|
|Timaliidae||Immaculate wren-babbler||Pnoepyga immaculata|
|Psittacidae||Derbyan parakeet||Psittacula derbiana*|
|An asterisk signifies that the species' range is limited to this ecoregion.|
Four species are shared with the adjacent ecoregions, and two are strict endemics limited to this ecoregion. These two species-buff-throated partridge and Derbyan parakeet-are known only from the sub-alpine conifer forests in the northeastern part of Arunachal Pradesh (Grimmet et al. 1998).
The ecoregion's other birds also include the globally threatened Tibetan eared-pheasant (Crossoptilon harmani) and Sclater's monal (Lophophorus sclateri) (IUCN 2000). Several other species, such as some of the pheasants, tragopans, and partridges-blood pheasant (Ithaginis cruentus), Blyth's tragopan (Tragopan blythii), Satyr tragopan (Tragopan satyra), Ward's trogon (Harpactes wardi), and chestnut-breasted partridge (Arborophila mandellii)-are characteristic of these sub-alpine Himalayan forests and have low disturbance thresholds. Therefore, they should receive conservation attention and can be used as focal species to monitor habitat integrity. Two large birds of prey, the lammergeier (Gypaetus barbatus) and the Himalayan griffon (Gyps himalayensis), which soar high above the mountains in these alpine regions and embody the aura of the large open spaces of the high Himalayas, are space-dependent species that should be conservation targets.
The ecoregion overlaps with two EBAs, Eastern Himalayas (130) and Southern Tibet (133), which have been identified by BirdLife International as important areas that harbor birds with limited breeding ranges (Stattersfield et al. 1998). Between them, these two EBAs contain twenty-four such restricted-range bird species.
Only about a third of the ecoregion's natural habitat has been cleared or degraded. Most of the remaining habitat occurs in large, contiguous blocks. The fourteen protected areas in the ecoregion cover more than 6,000 km2, or about 22 percent of the ecoregion's area (table 3).
Table 3. WCMC (1997) Protected Areas That Overlap with the Ecoregion.
|Protected Area||Area (km2)||IUCN Category|
|Annapurna Conservation Area||980|
|Langtang National Park||260||II|
|Makalu-Barun Conservation Area||350||II|
|Kulung Chhu WS||850||IV|
Ecoregion numbers of protected areas that overlap with additional ecoregions are listed in brackets.
Some of these protected areas-Langtang, Makalu-Barun, Black Mountain, and Sakteng-extend across several ecoregions and exceed 1,000 km2 in area. Annapurna and Jigme Dorji also extend across multiple ecoregions but are much larger, exceeding 4,000 km2. More importantly, several of these protected areas will be linked by natural habitat and included within conservation landscapes designed to maintain the altitudinal habitat continuity (WWF and ICIMOD 2000).
Types and Severity of Threats
Threats to the ecoregion's remaining natural habitats stem mostly from cutting trees for fuelwood by the local people and by tourist trekkers and mountaineers. In some parts of the ecoregion, fires are set to clear juniper forests and create grasslands for livestock grazing. Musk deer and Asiatic black bear are hunted for their musk and gall bladder, respectively.
Justification of Ecoregion Delineation
We used the Kali Gandaki River, widely considered a biogeographic barrier that defines the eastern and western Himalayan biotas, as a boundary to separate the sub-alpine conifer forests that extend across the length of the Himalayas into western and eastern ecoregions. We then used digital forest cover maps from MacKinnon (1997) to identify the distribution of the conifer forests, bordered by alpine meadows and broadleaf forests to the north and south, respectively. The belt of sub-alpine conifer forest to the east of the Kali Gandaki River was then placed in the Eastern Himalayan Sub-Alpine Conifer Forests [IM0501]. All the Himalayan ecoregions are part of Udvardy's Himalayan highlands biogeographic province.
Prepared by: Gopal S. Rawat and Eric D. Wikramanayake, with contributions from Pralad Yonzon
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