Sikkim - Impressions of a Botanist and a Description
of the Vegetation of the Singalila Ridge
L. K. Wade, Ph.D., North Vancouver, British Columbia
Paper presented to 1975 Annual Meeting at Bellevue, Washington
As another in a short series of articles by members of last year's Sikkim expedition led by Mr. and Mrs. Britt Smith, my contribution deals with a botanist's first impressions of that fascinating part of the world, and attempts as well a description of the general vegetation encountered along the trek, where possible in an altitudinal zonation sequence. I have not included the usual background information in this article, as this has already been covered by others in this series.
For all practical purposes our expedition began in the picturesque hill town of Darjeeling, a town straddling a narrow 6500 - 7500' high ridge above the Great Rungeet River. This ridge is a spur trending northwards from the great east-west oriented mass of Sinchul. Darjeeling, cut off thus from the Indian Plains, in effect faces the inner Himalaya, crowned in this part by the glorious massif of Kangchenjunga 45 miles to the northwest. In Darjeeling itself, as in most cities and towns the world over, introduced plants outnumber native ones in both diversity and mass effect. Nowhere is this feature more apparent than in Darjeeling, however, for here considerable visual impact and no small part of the actual character of the town is provided by the presence of thousands of large trees of the Japanese conifer Cryptomeria japonica, their dense pyramidal forms everywhere framing the quaint architecture of the town. So natural a part of the landscape do they appear, as do the exquisite pink South American Zephranthes robusto lilies that color the hillsides in this part of the world, that it is difficult to realize that they are aliens.
Introduced plants aside, the first profound impressions gained by the visiting botanist to this part of the Himalayas are twofold. The great species diversity is one of these as even the most casual study of any overgrown hillside on the outskirts of Darjeeling turns up a wonderful assortment of fascinating plants. Such curiosities as Arisaema costato, a Jack-in-the-Pulpit with deep wine-colored, white-veined spathes, and the green-flowered Arisaemo tortuosum vie for the botanist's attention with such beauties as Coelogyne cristata, a fragrant white epiphytic orchid, large trees of scarlet-flowered Rhododendron arboreum and small shrubs of Rhododendron lindleyi, the latter often festooned with fronds of a scrambling fern, Gleichenio volubilis.
The second very forceful impression is that of the curious mixing or overlap of familiar, purely temperate zone families and genera, which would look quite at home in the forests of the Pacific Northwest, with plants belonging to tropical and subtropical groups. The ancestors of these latter plants originated in the tropical floras of lower elevations, but have proved able over the millennia to penetrate to varying extents the higher elevations and survive. Thus we see what at first sight appear to be rather improbable combinations, such as groves of Himalayan Alder (Alnus nepolensis), their north temperate aspect modified by the presence of epiphytic orchids along their branches or by the occasional tree fern in their midst. In other spots equally boreal birches touch branches with enormous tree rhododendrons whose large evergreen leaves proclaim their origin in much milder climes. This overlap of temperate and tropical zone floras occurs wherever sufficiently high mountain ranges are found in tropical or subtropical latitudes, but perhaps nowhere else does it occur on such a grand scale as in the Himalayas. Here the vertical distances are so great and the floras so rich and diverse that the complexity of the resulting altitudinal zonation of the vegetation seems of a different order of magnitude to that found on most ranges. The extension of tropical plant families into the temperate zone altitudes was commented on in 1848 by Sir Joseph Hooker during his extensive travels in Sikkim. He attributed the phenomenon to "the uniform temperature and humidity of the climate.
From the Darjeeling area we traveled by Landrover about 30 miles west to Sandakphu, situated at 12,000' on the exposed crest of the Singalila Ridge, which is also the border between India and Nepal. This great ridge is north-south oriented, and terminates in the north with the great peak of Kangchenjunga. The drive was memorable from many points of view; the incredibly narrow, tortuous and unbelievably steep cobblestone road, the interminable check-points, the chameleon-like weather, and the vegetation we passed through. The last included a little of everything; low ridges and valley bottoms complete with bananas, Pandanus trees and other subtropical vegetation, oak and Magnolia campbellii forests at somewhat higher elevations, Arisaema and bamboo studded meadows, and patches of rhododendron forest in which we had tantalizing glimpses of Rhododendron falconers and R. cinnabarinum in full bloom. The final five miles or so of the drive led through rather open sub alpine country rich in temperate zone genera.
The Vegetation of the Singalila Ridge
As our trek proper began at Sandakphu, which at 12,000' was the highest point reached, I shall attempt to describe the vegetation "from the top down" in an altitudinal sequence beginning with the sub alpine vegetation around Sandakphu.Sandakphu lies atop the Singalila ridge in a very exposed position and receives the full benefit of winds sweeping across the ridge from Nepal. The landscape is very striking and the vegetation what we would classify in British Columbia as sub alpine parkland, an upper more open extension of sub alpine forest. The general aspect in the more exposed areas is open, a mosaic of grassy herb rich meadow, bamboo thicket, and a dense scrub of Rhododendron campanulatum. Scattered through this mosaic are small groves or picturesque solitary specimens of Abies spectabilis, a fir unparalleled for artistic form. Each individual seems to possess a character of its own, while small groves of these trees, characterized by their long, almost horizontal branches upswept towards the tips, make unforgettable pictures. At 12,000' on these exposed ridges Abies spectabilis averages about 40' tall but is often somewhat shorter
The open grassy areas are rich in herbaceous species amongst which blue and white forms of Anemone obtusilobo were in full bloom and quite common, as was a tiny blue Gentians with rather flat flowers, very similar to high altitude New Guinea species. Iris was common but not in flower, while in boggy patches Primula calderiana, a dwarf purple flowered species, brightened the scene. Other herbaceous genera noted in the grassy areas included Fragaria, Gnapholium, Artemisia, and Potentilla. The bamboo thickets appeared dominated by a single species, probably Arundinaria aristota, a pretty bamboo, 3 to 6' high, forming. thickets dense enough to exclude most other species. Here and there rock outcroppings intruded upon the landscape and around these in the most exposed areas were usually found low thickets of the dwarf Rhododendron lepidotum with its tiny dark grayish-green leaves, unfortunately not in bloom at the time of our visit. This species was seldom more than 3' high and was often accompanied by a beautiful red-berried Cotoneaster (probably C. microphylla) which formed extensive mats much like those formed by dwarf Coprosma species in the southern hemisphere. The thickets of mauve flowered Rhododendron campanulatum mentioned earlier averaged 4 - 8' tall and often sheltered other shrub species, amongst which one in particular stood out, Daphne bhuluia, pink-flowered, sweet-scented and up to 10' tall. A small Berberis, leafless this early in the season, was abundant everywhere. To add to this brief sketch of the "sub alpine parkland" we had only to drop 100' or so below the most exposed portion of the ridge to find in these slightly sheltered locations both Rhododendron arboreum and R. barbatum, the brilliant red flowers of both adding flashes of color to a landscape made somber by almost constant swirling mist and rolling cloud.
From Sandakphu we hiked north along the Singalila Ridge to Phalut,a distance of about 14 miles. As Phalut lies at about 11,500', we saw considerably more sub alpine vegetation similar to that just described. The path often dipped close to 11,000', however, giving us an opportunity to witness quite striking changes in the vegetation. Perhaps the most obvious of these changes was the increasing density of the firs encountered almost as soon as we dropped below the most exposed ridge tops. Below about 11,600' Abies spectabilis formed sub alpine forest rather than parkland, although the forest was still quite open in aspect and many small quite treeless areas were still evident, some no doubt man-made. At this elevation the trees were taller, some in the neighborhood of 70' or more. We passed through some beautiful almost pure stands of this lovely fir, the dark green foliage often set off by the scarlet blooms of large solitary Rhododendron arboreum trees. Abies spectabilis is said to extend down to about 10,000', although we did not encounter any at that low an elevation. The most spectacular change encountered below about 11,800' was the appearance in sheltered valleys and draws of small groves and later whole "forests" of Rhododendron hodgsonii, (See July 1975, for R. hodgsonii photographed in Sikkim on the trek) very striking with its immense leathery leaves, brilliant pink to rose flowers and smooth mottled grayish-pink bark. This species continued to amaze us with its color variations and size, some groves averaging 25 - 30' tall, and studying it occupied much of our attention. In addition to the increasing abundance of Rhododendron arboreum and barbatum, we also encountered the Himalayan Birch (Betula utilis) for the first time. This is an extraordinarily lovely species with brilliant orange-red exfoliating bark, in texture rather like a cross between Physocarpus capitatus (ninebark) of our Pacific Northwest forests and the cultivated Acer griseum. The effect of this birch was made even more beautiful by the presence of abundant pendant lichens along its branches. Southern Sikkim experiences an annual rainfall in excess of 200", a fact made quite obvious not only by the almost ever-present swirling mists, but by the very high prevalence of epiphytic mosses, liverworts, lichens and ferns on the tree branches and trunks. These hang in sodden splendor in great pendant masses or pillow-like clumps, giving a ghostly effect to the trees on which they grow. This effect is heightened as the trees are often not seen until the last moment when they are suddenly apparent half silhouetted against a constantly shifting pattern of mists. As the great ranges in Sikkim tend to be north-south oriented rather than east-west oriented as elsewhere in the Himalayas, the monsoons are not blocked by front ranges and extend as a result deep into the Sikkim Himalaya right to the southern slopes of the great peaks walling off the Tibetan Plateau. This orientation gives a perpetually very wet Sikkim the well-earned title of "land of mist", a situation often alluded to by both White and Hookker, among other writers.
From Phalut our route led up and over the Gosa Pass, 12,500' high and the site of the triple border between India, Nepal and Sikkim. Unfortunately the entire ascent to the pass was made in thick cloud and we saw little other than numerous specimens of Primula denticulata growing in moist peaty areas beside the steep narrow path. These primulas were no more than 8" high and looked quite stunted compared to the same species in cultivation. From this high point an often spectacular mountain trail led very steeply downwards a full 2000' through the various vegetation zones already described. At 10,500' the vegetation changed abruptly and dramatically, the sub alpine forest with its fir and Rhododendron hodgsonii giving way to dripping montane rain forest dominated by Rhododendron falconeri. There was surprisingly little attitudinal overlap between these two large-leaved species, R. hodgsonii giving way to R. falconeri over a vertical transition of a few hundred feet. At this transition from sub alpine to montane forest an enormous increase in species diversity takes place and this was most apparent along the last few miles to Chiwabhanjyang, our first night's stop in Sikkim itself. Here an incredible vegetation presented itself. The tree canopy consisted of enormous specimens of Rhododendron falconeri in full glorious bloom along with maples and the white-flowered tree-sized Viburnun cordifolium. Rhododendron cinnabarinum arched over the path and R. arboreum was still with us in the form of occasional individual trees. The understory was populated with many shrubs, including Viburnum, Daphne, Pieris, Mahonia, Berberis, Roso sericea, (one of only two four-petaled roses), and a bright yellow Crotolaria, the only leguminous shrub we saw in the Singalila Ridge country. The last, along with the rose, was abundant later on, particularly on cleared hillsides at 9000-10,000' elevations. The herbaceous layer in the montane forest was exceedingly rich too, one of the most common and certainly most obvious species being Arisaema griffithi with massive leaves 3' high and wide hood-shaped wine and yellow spathes, the whole effect both pleasing and bizarre. The spathes were so hard and shiny as to give the impression of being made of plastic. Along with these giants we found a smaller and more delicate relative, Arisaema nepenthoides, whose species name was inspired by the superficial resemblance to the spotted and streaked flowers of Nepenthes, the genus of pitcher plant common to southeast Asia. Violets and strawberries were common in the grasses and a delicate pink flowered Vaccinium cascaded in masses down dripping rock faces. The whole aspect was one of the most beautiful I have ever encountered, and it was made even more so by the abundance of delicate epiphytes, among which filmy ferns (Hymenophyllum spp.) now made their first appearance.
The following day we walked from Chiwabhanjyang to Jaribotey, both at about 10,000' with undulating country between. Montane rain forest predominated, but in places the path led high enough for encounters with the Rhododendron hodgsonii forest again. The montane rain forest had some interesting variations from that previously seen. Epiphytic ferns were even more abundant with Hymenophyllum and Grommitis particularly common. In one open glade we were treated to the sight of masses of the giant lily Cardiocrinum giganteum, one of the most famous plants in this part of the world. The flowering stalks, which would eventually reach 8' and more high, were at this stage only about 4' high and of course in tight bud. Aconitum, Primula, Viola and Lignariella were everywhere, although the Aconitum and most of the Primula species were not yet in bloom. Primula gracilipes, an exquisite dwarf purple species, was in full bloom at this season and its rosettes were often seen nestled in moss bolsters along stream banks, one of the prettiest small species we saw on the entire tip. At 10,000' the last of the Abies has been left behind to be replaced among conifers by occasional groves of a spectacular large hemlock, Tsuga dumoso. Like so many species of this region, this one is really superlative with massive trunks 6 - 8' in diameter and lovely feathery foliage composed of needles about twice as long as those of our native Western Hemlock (Tsuga heterophylla). Where hemlock dominated the ground underneath was relatively clear, reminding me of some of the eastern North American forests of Tsuga conadensis. Pure stands appeared rare, however, occasional trees mixed with angiosperm trees being the rule.
At 9500 - 10,000' oak forest was encountered and this forest type, with innumerable local variations, dominated most of the route all the way to Hilley at the end of our trek. The dominant tree of this forest was Quercus lamellosa, an enormous evergreen species whose massive trunks rose from the forest floor in mist-shrouded grandeur. The acorns do not fall singly, but rather in grapefruit-sized clumps and are so numerous as to cover the forest floor. Many other trees are abundant in this forest as well and include Lithocorpus species (Tanbark Oak), Castonopsis, Acer pictum and Acer campola, both very beautiful maples, and below about 9500' Magnolia cambellii and Rhododendron grande, the last showing its beautiful silvery new growth. In places this species formed an almost solid understory beneath the oaks, giving way here and there to small clumps of a pretty forest bamboo or to ferns such as Pteris, Dryopteris and Osmundo. Epiphytic specimens of Rhododendron dalhousiae were often seen perched artistically on the oak and Castanopsis branches, their perfume scenting the surrounding forest
This oak zone was the lowest zone that we walked through and hence had a chance to look at reasonably carefully. Below 9000' we had only glimpses at periodic stops along the road. This was enough, however, to note large plants of Rhododendron griffithianum growing in a leach-infested forest at about 7500' amidst cherries, hemlock and oaks, and lower down at 5000' the famous Yellow Raspberry (Rubus ellipticus) growing with two interesting Ericaceae, a white-flowering Lyonia and a beautiful epiphyte, Agapetes serpens. The latter has pendant, bright red lantern-shaped flowers about 1" long which spring from a rather skeletal branching structure. They are one of the choicest Himalayan plants and close relatives of the blueberry genus Vaccinium.
Brief as this description of the vegetation of the Singalila area is, I trust it will convey some idea of the spectacularly lovely vegetation that clothes these beautiful ridges and slopes and will also give a glimpse of one of the world's richest temperate zone floras.