The epiphytic ferns of Kikuchi Gorge, Kumamoto Prefecture, Japan

Kyushu’s naturally wet climate and relative warmth provides near perfect growing conditions for epiphytic plants and few places rival one of its greatest natural wonders, Kikuchi Gorge in northern Kumamoto Prefecture. This gorge drains an upland plateau averaging between 600-800 meters elevation. The water of the gorge’s river, as well as many of the region’s waters, are some of the purest in Japan since their source is subterranean, and therefore is filtered through kilometers of porous rock.  The entire area is in fact the base of an ancient volcano that blew its top thousands of years ago, leaving behind one of the world’s largest extant calderas, Aso Caldera, measuring 25 km in diameter north to south, and 18 km east to west.  Though the mountain lost most of its mass in the distant past, it remains active.

Along the watercourse of the gorge are numerous waterfalls and old growth forest.  This forest is most famous for its fall foliage, in particular its maples and zelkovas, but also is home to a host of many types of fern and their allies, the clubmosses and spikemosses.  Without a doubt, historically the gorge boasted many epiphytic orchids as well, but these are few and far between nowadays, most likely having been collected out years ago.  In the 60’s, 70″s, and 80’s, as Japan’s economy flourished, the desire for rare species reached a fevered pitch and many wild areas were denuded of their most precious citizens – orchids lead the way, but many others were effected.  Luckily, most ferns were left alone, or were able to reproduce fast enough to maintain viable populations.  Kikuchi Gorge remains a lovely example of epiphytic laden, riparian old growth forest.

Epiphytes seem to grow most luxuriantly on horizontal branches where leaves, animal droppings, and other organic material can build up.  Two commonly seen ferns in the gorge are Loxogramme salicifolia and Lemmaphyllum microphyllum, as seen in the picture below.  The long simple fronds belong to L. salicifolia while the small oval fronds are of L. microphyllum. The latter is a very common species throughout the low mountains of Kyushu, while the Loxogramme is more rare.  In the Fukuoka City area I’ve seen L. salicifolia growing strictly on rocks, but in Kikuchi the humidity is so high that it ventures out onto the trees as well.  Like many other epiphytic ferns, this species shrivels when dry, only to rebound once the rains come again.

Another common epiphytic plant is Selaginella involvens, not a proper fern, but rather a spikemoss, in the family Selaginellaceae.   Like the Loxogramme, this species shrivels in dry weather.  S. involvens is a common lithophyte in the Fukuoka City area, but rarely an epiphyte. In this gorge it covers almost any sizable tree and accounts for the lion’s share of the epiphytic biomass. You can see that there had been little rain when this photo was taken, as evidenced by their curled up fronds. Other species in the photo include the classic fern shaped fronds of Polypodium nipponicum and the drooping fronds further out are the Loxogramme again.

The most spectacular fern of Kikuchi Gorge is Polypodium nipponicum.  Those familiar with the common P. vulgare may at first be unimpressed, but this species is a real treat to see in person.  Each frond can grow to 25 or more centimeters and the trailing rhizome is a curious silver-blue green color. The fronds too are soft to the touch, covered in a fine pubescence.  Of the ferns still in abundance here, this one has been the most collected.  Kikuchi Gorge is visited in the summer and fall months by literal hordes of people and few places along its banks are free of prying hands.  Not surprisingly, virtually all plants of P. nipponicum there today are just out of arms reach – a testament to the desirability of this species.  Luckily, it still festoons the higher branches and boles of the stream side forest.

Vittaria flexuosa is another common lithophyte (meaning growing on rock) in the Fukuoka City area, however it is found growing epiphytically here as well.  It is a somewhat unlovely fern, much like the lowland growing Lepisorus thunbergiana, but with much longer, thinner fronds that are always dark green in color.  These commonly reach or even exceed 50 cm in length, hanging down in tufts, and give the plant its fanciful English names – shoestring fern, grass fern, beard fern, and ribbon fern.  Its Japanese name, shishiran, is much more regale, meaning “lion’s mane orchid”.  Though not a lovely plant, it certainly is a novelty.

A real treat was seeing one of Japan’s rare epiphytic clubmosses, Lycopodium sieboldii.  This plant is found only in the wettest forests of southern Japan, as far north as the eastern seaboard of Honshu south of Tokyo.  It is another desired and oft collected epiphyte.  I saw only this one specimen hanging off a slender vertical branch some 15 meters above the river and its many rocks – no doubt the reason it remains in place today.  I’m sure these were much more common in years past.  While many people are familiar with the little clubmosses found underfoot in temperate forests, in the subtropics and tropics of the world they have taken to the trees and some species can grow several meters in length.  L. sieboldii is a fairly modest plant by comparison, and yet its cascading branches covered in scale-like leaflets can attain lengths of 50 cm or more.  It endangered throughout its range in Japan, and is reported to be extinct in Fukuoka Prefecture, where I live.

Check out this video on the epiphytes of the gorge up close and personal:

Amazingly, I saw no epiphytic orchids. In a way that is not surprising since they all no doubt were removed from this lovely place years ago. It seems that all famous forests and mountains have been stripped of them utterly, based on my limited wanderings. To see them you have to go to places people usually don’t go. I know that Dendrobium monilforme is said to yet live here, and likely others exist in hard to reach (and see!) places.  Two terrestrials are easy to see though, the relatively common Calathe reflexa and the rare and tiny jewel orchid, Goodyera biflora (syn. G. macrantha).

Other epiphytic ferns seen here include Lepisorus onoei, Neocheiropteris subhastata, Colysis elliptica, and Crypsinus hastatus. There also was one I couldn’t identify, but looked like a Deparia that likely is not found growing epiphytically in drier habitats. Surprisingly absent were any Pyrrosia species, even the common P. lingua. This forest would be perfect habitat for Pyrrosia hastata and indeed it probably does exist somewhere in the gorge. Likewise the very common Lepisorus thunbergiana is apparently absent or at least inconspicuous, perhaps due to the elevation. Another possible resident could include the rare winter green, summer dormant Polypodium fauriei.

In the future I hope to get a better look at this special place.  The over-used trails end further upstream from the main waterfall area and likely are home to more interesting plants, unharnessed by the masses of summer visitors.  Hands down, this place has the nicest epiphytic plant community I’ve yet seen on Kyushu, though the forests of Miyazaki and Kagoshima Prefectures may very well harbor even better ones.  Despite the cutting of primeval forest and over collection of rare plants, Kyushu remains a wonderful place to botanize.