The Ferns of Northern Taiwan

Unlike the larger groups of mountains which ring Taipei, such as the Mt. Tatun and Mt. Kuanyin groups, the Nankang Hills lie within the city limits, and cover a small enough area to walk in a day. The long ridge of Nankang Hill (Nankangshan) and Thumb Hill (Muchihshan) is flanked to the west by the "Four Animals": Tiger Hill (Hushan), Panther Hill (Paoshan), Lion Hill (Shihshan) and Elephant Hill (Hsiangshan), each between 100 and 200 meters high. Even when the hills are shrouded in drizzle brought in by the northeasterly monsoon, there is a steady stream of visitors walking their paths.

The Bodhisattva's turnip

Turning from Hsinyi Road, with its closely packed apartment buildings, onto the Elephant Hill trail, even along the first short stretch of steps one can see at least 30 different species of ferns among the green trees and bamboos.

The most eye-catching is the turnip fern (Angiopteris lygodiifolia), whose two to three-meter long fronds give it a highly tropical air. When its fronds fall they leave behind hand-sized stumps all around the base of the plant, giving the appearance of a lotus flower, and this earns the turnip fern its rather more poetic Chinese name of Guanyin zuo lian, meaning "the Bodhisattva Guanyin seated on a lotus throne." Nestling beneath it are several Pteris semipinnata, with fronds a meter long, on which each pinna (leaflet) looks as if half of it has been cut away, producing a beautiful asymmetry. To one side, a two-meter tall tree is entwined by the vine-like Japanese climbing fern (Lygodium japonicum). Most climbing plants spread by unlimited growth of their stems, but in the case of the climbing ferns it is the fronds which continuously grow longer, giving them the longest leaves of any plant. These fronds are very thick and tough, and in the past people used to tie sections together to make brushes for cleaning woks. Even today in Taiwan one can still buy wok brushes made from Japanese climbing fern.

Following the winding footpath, beside a wall of loess halfway up the hill are several Cibotium taiwanense, with their thick, heavy fronds hanging down towards the valley like enormous fans. At the base of their leaf stalks they bear velvety golden scales, which earn the fern its local name of "golden dog fur." These scales protect the growing parts of the plant, and some believe they also collect water to help the ferns survive dry periods. Before the advent of modern medicines, C. taiwanense served previous generations as an effective haemostatic medicine, used to stop bleeding.

Jurassic Park

Halfway up the precipitous northwest side of Elephant Hill the air is especially damp, and clinging to the slopes are many moisture-loving ferns such as Diplazium subsinuatum, the wood fern species Dryopteris sparsa, and the bat's wing fern (Histiopteris incisa), which has fronds that stand out in pairs like wings. Down below, the tall buildings of Taipei's Hsinyi District, where land costs several hundred thousand NT Dollars a square meter, are in clear view. But on top of the hill the ground is densely covered with tall "flying spider-monkey" tree ferns (Cyathea lepifera), and the shorter Cyathea podophylla, which can barely support the weight of its enormous fronds.

Tree ferns can grow as much as 10 to 20 meters tall, and they look much the same as the primitive ferns of the Paleozoic era and the dinosaur age. For the garden designer, a tall, broad tree fern can create a tropical hothouse atmosphere. Along a few hundred meters of path running up Elephant Hill, the thousands of C. podophylla, fish fern (Blechnum orientale) and flying spider-monkey fern give the hillside the appearance of a "Jurassic Park," which, set against thecrowded tower blocks down below in the city, creates a bizarre juxtaposition of the primitive and the modern.

In fact, this may be a unique scene anywhere in the world, because forests of flying spider-monkey ferns are found only in the lowlands of northern Taiwan. In the past, Taiwan exported large numbers of desk tidies made from this tree fern's heartwood. When international trade adjudicators came to Taiwan to solemnly investigate the alleged overcropping of a rare plant, they were surprised to find flying spider-monkey ferns growing everywhere. Though seen internationally as a scarce resource, the plants were two a penny in Taiwan, so the threatened trade sanctions were dropped.

Geriatric plants

For the reasons why flying spider-monkey ferns have such a strong preference for Taiwan, we have to go back 400 million years. The non-flowering ferns were the dominant plants of the Paleozoic world, but with climate change they were gradually edged out of this role by the gymnosperms and then the flowering plants, which are better adapted to dry climatic conditions. Eventually, the ferns were relegated to the forest floor.

In the ice ages, which ended over 10,000 years ago, East Asia was largely spared the glaciation which enveloped Europe and North America. Japan, Taiwan and central and southern China became refuges for Asian flora and fauna, and also home to many glacial relict plant species.

With its special geography, little Taiwan was a magnet for ferns, attracting over 600 species. Ferns propagate by releasing powder-fine spores. Taiwan is situated at the eastern edge of the Asian continent, and on the climate map it straddles the southern edge of the temperate zone and the northern edge of the tropical zone. Throughout the year it is visited in turn by southwesterly air streams, typhoons and northeasterly monsoon winds. Fern spores blown across the sea found all kinds of perfect niche environments amid the varied topography of this little isle bristling with mountains and hills. This is why Taiwan's ferns far outnumber Europe's hundred or so species and North America's 400-odd species. Various East Asian regions such as Japan, China's Yunnan Province and the Philippines have more fern species than Taiwan. But considering Taiwan's small area, the density of species here means it is really no exaggeration to call it a "fern kingdom."

A combination of favorable natural conditions have also given ferns in Taiwan an "accessibility" not matched in other regions. In Japan, the flying monkey-spider fern is a mountain dweller, but in Taiwan it grows in the plains, and is one of the commonest green plants to be seen in the countryside of northern Taiwan. In the Philippines Dipteris conjugata, a fern found in many Asian countries, hides away in sparsely populated mountain areas. But one Swiss botanist who had thought he would only ever see D. conjugata as collected specimens was so delighted when he came to Taiwan's Yangmingshan and found himself surrounded by D. conjugata growing wild there that he almost got down on his knees to give thanks.

Fern heaven

After fern spores fall to the ground, they need plenty of moisture to help them germinate and grow. This is why the Nankang Hills, shrouded in the year-round damp of northern Taiwan, is home to a fifth of Taiwan's fern species.

The Nankang Hills stretch across the Taipei Basin as a straight finger of low sandstone peaks 140-370 meters high. Their highly uneven topography, carved out by the abundant local rainfall, has meant that despite lying cheek by jowl with the city, they have been spared destructive overdevelopment and have been able to maintain a basic forest environment. The hills' great diversity of microenvironments creates a paradise for ferns. In an area of a similar size and topography in central or southern Taiwan, one would often find only 50 or so different fern species.

The Nankang Hills present a microcosm of fern ecology at medium to low altitudes in Taiwan. There one can find everything from the spider brake fern (Pteris multifida) and parsley fern (Sphenomeris chusana), which are often seen in cities, to wedge-leaf spleenwort (Asplenium cuneatum), which usually grows at medium altitudes around 1500 meters. Near the hiking map put up by the Taipei City Government at the Hsinyi Road entrance to the Elephant Hill trail, in an area of relatively arid secondary woodland on the lowest slopes of the hill, the East Indian holly fern (Arachniodes aristata), which is mainly found in central and southern Taiwan, can also be seen in all its splendor.

One person who has long been studying the ferns of the Nankang Hills is Mou Shan-chieh. Over a decade ago, while a student in the botany department at National Taiwan University, he discovered the richness of the fern ecology there. After finishing his studies he moved to a house not far from the Nankang Hills, so he began surveying the area's ferns. To date he has recorded over 120 species there. Because of the different environments on each of the Four Animals Hills, Thumb Hill and Nankang Hill, one can see different species of fern along the trails on each of them.

Separate domains

After climbing to the top of Elephant Hill from Hsinyi Road, if we move on towards Thumb Hill and Nankang Hill, the fern population is already somewhat different from on the slopes of Elephant Hill. On the ridge which connects Elephant Hill with Nankang Hill, there are traces of human activity left behind from the period of Japanese rule. A large stand of artificially planted Formosan koa (Acacia confusa) sway and rustle in the cold, gusty wind. The dry soil of the exposed ridge is far from an ideal growing environment for ferns, yet hidden under the koa trees is a single Diplazium petri, which is a rare specimen in this area. After discovering it seven or eight years ago, Mou Shan-chieh has not found any more.

Below the ridge, out of the wind, we find Tectaria decurrens, Diplazium bantamense, and also Christella latipinna, of which there are only 100-plus plants in the area.

Walking down into one of the valleys below Thumb Hill, in an especially damp and shady spot where several streams flow, the Java fern (Microsorium pteropus), a favorite aquarium plant, grows in the babbling water. Hiding on the damp earthy slopes is also Microlepia krameri, which is unique to Taiwan, and was discovered as a new species in 1985 by a Taiwanese botanist.

Not only do different fern species grow on each hill and in each valley, but even within a single valley, differences in microclimate clearly reveal different fern species' preferences. To take the tall tree ferns as an example, the ridges, where water does not easily collect, is usually the domain of the flying spider-monkey fern, whereas the spiny tree fern (Cyathea spinulosa) quietly reigns lower down in deeply shaded spots. Under the many-layered canopy of the large trees, occasionally there is a glade open to the sky, and here the lace fern (Microlepia strigosa) and the limp-leaf fern (Microlepia speluncae) seize the opportunity to display their proud green in the bright sunshine.

Walking ferns

As ferns do not flower, they cannot compare with the bright colors of the flowering plants, but instead they attract us with their leaves. The tightly curled "croziers" of the young fronds gradually unfurl and grow into all kinds of strange shapes, such as the peacock-tail spread of the spider brake fern, or the spine-like protuberances along the leaf edges of Bolbitis appendiculata. By contrast, the whisk fern (Psilotum nudum) has no fronds at all, but creeping stems shaped just like pine needles.

Ferns with "dimorphic" fronds grow two completely different kinds of leaves. For instance, the green penny fern (Lemmaphyllum microphyllum), which attaches itself to rocks and tree trunks, has succulent, round "feeding leaves" which absorb nutrients, and also long, thin "fertile leaves" which are responsible for reproduction. The two look very different, and have different functions. They often mislead people into thinking they are seeing two different species of plant.

This journey of discovery into the fern world seems to reveal the skill and wisdom of the creator. Bolbitis subcordata is one of the many "walking ferns": at the ends of its fronds it grows brown "adventitious" buds, and when the fronds grow long enough to touch the ground, these buds take root and grow into new plants. Thus, as well as reproducing by means of its spores, B. subcordata also uses its adventitious buds to march into new territory.

With ferns' growing popularity as garden plants, Taiwan's wild fern species have attracted increasing attention. Last year the Nature Trail Association Taiwan set up a "Taiwan Fern Club." As well as going all over Taiwan to survey fern species, the 20-odd members also organize fern appreciation events at weekends and holidays, to help other people get to know our native fern species. Besides introducing participants to the beauty of ferns' fronds, the guides take along magnifying glasses to let everyone see the world of their sporangia (spore-bearing sacs).

Fern friends

On one such fern outing, Taiwan Fern Club organizer Lu Pi-feng first teaches the groups how to recognize different fern species along the way by the shape of their fronds, and then, with the help of the magnifying glass, to appreciate the extraordinary diversity of the sori (groups of sporangia) on the fronds' undersides. Under the lens, the arrangement of the sporangia appears different in every fern species. In Cibotium taiwanense, each sorus is covered by an indusium (protective covering) made up of two flaps of tissue in the shape of a cockle shell, which splits slightly open to release the spores; the false staghorn fern (Dicranopteris linearis), produces single bead-like sporangia arranged in their sori in a plum-flower pattern.

As well as helping people get to know and appreciateTaiwan's ferns, in view of the previous lack of adequate basic surveys of local ferns the Taiwan Fern Club also hopes to record the fern species all over Taiwan, in order to provide basic ecological data. The year before last, the United Nations nominated over 20 ecologically important areas worldwide as biosphere reserves, to be the subject of major conservation efforts with the support of the international community. But although East Asia was recognized as one of the regions of greatest biodiversity, a lack of detailed species lists and ecological background data prevented many areas being listed.

Besides the long-term tasks of surveying and classification, the Taiwan Fern Club also hopes that their efforts to educate the public to recognize and understand ferns will also encourage people to go on to "protect" the ground beneath their feet. Fern classification expert Mou Shan-chieh says that the greatest threat to the ferns in the Nankang Hills area comes from the many "well-meaning" people, among those who come to exercise here, who clear away the "weeds"-i.e. ferns-from the paths and flat areas, and plant garden plants everywhere, so that the hills are now being colonized by introduced poinsettia (Euphorbia pulcherrima) and crown-of-thorns (Euphorbia milii).

Indomitable ferns

Coming down from the Nankang Hills, as this journey of discovery draws to a close, despite the traffic on the tarred road one can still glimpse on the hillside the oriental chain fern (Woodwardia orientalis), Osmunda banksiaefolia, and the pretty, tassel-like giant sword fern (Nephrolepis biserrata). As we approach the busy bus-stop area, surely we will not find ferns here too? But there outside a row of old-style apartment buildings, we spy the fronds of a maidenhair fern (Adiantum capillus-veneris) poking up out of a drainage channel. Unlike the delicate imported variety one sees at flower markets, this native maidenhair fern can often be seen growing on urban concrete or brick walls, or in drains.

This "ambush" by a maidenhair fern at the end of our outing surely serves to remind us: when city people devote so much time to tending exotic plants from all over the world, they shouldn't neglect the ferns at their very feet!

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Ctenitis subglandulosa-green, glistening and elegant. Myriad ferns in countless shades of green lend a primitive, tropical air to the wet mountain forests of northern Taiwan.

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(left:) The crozier of a tender young fern frond seems ready to fall like a huge green drip. (above:) As it gradually unfurls, it will grow into a lovely bat's wing fern (Histiopteris incisa).

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On one of the regular fern appreciation outings put on by the Taiwan Fern Club, a creeping Pronephrium triphyllum attracts fern lovers to gather around. (photo by Jimmy Lin)

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In the sunshine, the sori of Christella acuminata shine through its fronds like black pearls scattered on green silk.

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Ferns do not flower, but their fronds are

amazingly diverse and often strangely

beautiful. Shown here, from top to bottom: Dryopteris sparsa; the narrow fronds of Vittaria angusto-elongata; Cibotium taiwanense, shaped like enormous fans; Dipteris conjugata, with its palm-like fronds; Christella acuminata, sticking out long "tongues"; and a young Japanese climbing fern (Lygodium japonicum), pushing its way up out of a crevice in a stone stairway. As for the "imposters" lurking among the bright green bryophytes in the picture at bottom, the heart-shaped shoots are Lindsaea orbiculata var. commixta, while the leaf-shaped ones are parsley fern (Sphenomeris chusana).

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Pictured here, from left to right: Lindsaea orbiculata var. commixta; Dicranopteris linearis shoots; and the two different types of fronds of the green penny fern (Lemmaphyllum microphyllum). The fertile fronds (second from right) are like little spoons, while the feeding fronds (far right) look like melon seeds inlaid into the tree trunk.

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So close, yet worlds apart-the tree ferns which crowd the middle slopes of Elephant Hill look down on densely-populated eastern Taipei City with its sky-high property prices. City people who take the time to climb these hills can experience a journey into a primitive, natural world.