When you enter under the canopy of a conifer-broadleaf forest, you would involuntarily turn your attention to unusual plants with snailwise leaves. These leaves may be gathered in a cluster or, as in Dryopteris crassirhizoma Nakai – be arranged like a rosette. An old Russian legend is associated with these plants, saying that they bloom only one night. According to that legend, the strength and power of their flower is such that he who could tear off the flower would have nothing inaccessible or subject to him. Yet, it is common knowledge that ferns multiply by means of spores. Possibly, the very absence in those plants of flowers makes it difficult to distinguish their species by people other than botanists; hence, Pteridium aquilinum (L. Kuhn) is the only edible fern species.
Today, botanists have identified about 10,000 fern species widespread worldwide. Their highest diversity (4,500 species) is in the humid forests of Southeast Asia, the second center of specific diversity (2,250 species) being in tropical America. Of all the regions of Russia, the richest in ferns is the Russian Far East (98 species), most of them (60 species) being concentrated in Primorye.
Only two Primorye fern species are widely distributed geographically. One is Pteridium aquilinum (L. Kuhn), at present one of the few fern-like representatives characterized by a vast range. It is widespread over various regions of the Northern and Southern hemispheres, and is perhaps absent only in tundra and deserts. Pteridium aquilinum (L. Kuhn) may occur in meadow and forest plant communities in sites with highly different conditions of humidity and light. According to some researchers, such vast distribution of this species is caused not only by natural reasons, but also by man-made effects on nature. Having a deeply lying thick rhizome, Pteridium aquilinum can actively grow on felled, after-fire sites, abandoned fields and meadows. In some countries, this species is a weed plant hard to combat. Other Primorye fern species are not so widespread. Almost half of them have common geographic distribution within East Asia (Russian Far East, China, Korea, Japan). They are chiefly widespread in the moderate climatic zone. Yet, there are also species, which V. L. Komarov (1949) noted to be indigenously characterized by growth in tropical belt localities, their presence in moderately warm climate being secondary. Komarov assigns Coniogramme intermedia Hieron to those species. This unique fern, whose leaves are somewhat reminiscent of ash leaves, occur in Russia only in the Far East (southeastern part of Khabarovsk and Primorye territories, and Sakhalin Region), where it grows on the northern boundary of the range. Beyond Russia, the species is known in India, China, Korea and Japan. Given that the coniogram occurs seldom in the Russian Far East, the species has been entered in the list of rare and protected plants of the region (Kharkevich, Kachura, 1981).
In characterizing the geographic distribution of Primorye ferns, it should be noted that neighboring Japan boasts the largest number of species (54), and Korea and China have 45 and 35 species, respectively, in common with Primorye. Again, of Russia’s other regions, associations are closest with Siberia, which has twelve species in common with Primorye. These twelve species do not grow beyond Primorye, and seven of them only in the south of the territory.
Russian Far Eastern ferns do not occupy a prominent place in flora specific composition, but are quit e noticeable in the vegetation of cliffs, not infrequently creating an aspect on moist fields and meadows, and constitute a characteristic element of coniferous and conifer-broadleaf forests. The prevalent number of ferns grow on shaded and half-shaded sites, their structure corresponding to this lifestyle, given their large, considerably dissected leaves. These are mainly forest plants that may occur under the canopy of coniferous, conifer-broadleaf and broadleaf forests. As a rule, fern species are not associated with plant communities of specific composition. For example, the widespread Phegopteris coonectilis (Michx.) Watt.] commonly occurs in confer forests, is not infrequent in the grass cover of conifer-broadleaf forestrs, and grows on rocky banks and cliffs. And still, some fern groups may be found to be assigned to specific communities. For instance, Athyrium sinense Rupr., Lunathyrium pycnosorum (Christ) Koidz., and Dryopteris crassirhizoma may be called plants characteristic of conifer-broadleaf forests. The latter is also interesting in that its leaves winter green. In fall, when most herbaceous plants prepare for winter, and their ground portions wither away, Dryopteris crasirhizoma leaves lie down to stay live all winter. You can see them green among fallen leaves in early spring when the snow had just melted. Wintered leaves of this fern die off by the time new leaves had developed.
Under the forest canopy, you can also come across representatives of a small group of ferns that feel themselves better on open sites. An example is the Osmundastrum asiaticum (Fern.) Tagawa species of the ancient family, which blossomed in Mesozoic. Besides, it is characterized by the fact that its spores are located on specialized leaves. Those leaves (sporophylls) appear on plants in spring to live for a short time to die off instantly after spore maturation. They are brown, differing considerably from vegetative leaves in outer appearance and structure. Dense broad-oval light green vegetative leaves do not carry spores, and start to develop slightly later than sporophylls to die off in fall, like most herbaceous species.
Some fern species may occur on rocky detritus and cliffs, including some forest ferns and groups of species preferentially occurring on cliffs. In turn, of representatives of said group some were noted only on cliffs, and others on tree branches in the ground cover of coniferous forests. Ferns characteristic of cliffs are generally small in size and with short compact rhizomes that fasten themselves in rock cracks. This is the outer appearance of Woodsia ilvenis (L.) R. Br., a fern that may occur both within and beyond Russia. The fragrant Dryopteris fragrans (L.) Schott, another widespread Primorye fern species, grows on dry cliffs and rocky slopes. This plant has uniquely adapted itself to withstanding unfavorable conditions of lighted open cliffs. Its already dead leaves may stay for several years to protect the growing rhizome portion. Besides, there are special small glands on the leaves that secrete resinous substances, which along with numerous leaf-covering scales protect the plant against overheating; the species generally grows on sites with strong sunshine. Resinous substances have a strong and pleasant smell; that is why this Dryopteris species was called “fragrant”.
Many relict, ancient forms have remained in the group of Russian Far Eastern cliff ferns. The recent soft and humid Primorye climate allows such species to remain in unique “shelters” on moist cliffs, where they do not experience significant fluctuations of climatic and microclimatic factors, where competition from younger species is considerably lower. The peculiar “lifestyle” of relict species does not quite correspond to their structure and ecological demands. An example of such ferns may be the Gonocormus minutus (Blume) Bosch, which belongs to the unique Hymenophyllaceae family. Representatives of this family are chiefly inhabitants of tropical and subtropical countries, only few growing farther in the north. In Russia, this species occurs only in some districts of Primorye; abroad, it is known to grow in the Himalayas.
Gonocormus is a tiny (up to 2.5 cm tall) plant, resembling moss more than fern. Its short roots can suck in nutritive substances only from the substrate surface, and its gentle one-layer leaf plates have no stomas. All this is indicative of its adaptability to life in conditions of perpetually high air humidity. Gonocormus can endure slight air dryness; in this case, its leaves dry up, as it were, to again assume their usual form when the moisture content in the air rises. The plant responds similarly to arrival of cold: its fronds do not die off in fall, like do the leaves of most plants in the temperate zone, but remain under snow to unfold again with arrival of warm weather. The fact that Gonocormus belongs to evergreen plants once again underscores its relict nature.
Given the Gonocormus structure and its ecological and biological properties, one may assume that this species was once common for humid forests as an epiphyte on lower tree trunk portions. With lapse of time, climatic and phytocenotic conditions changed, and the fern was gradually displaced to wet cliffs, where it sometimes occurs today as well. It does not always withstand competition from neighboring mosses and flower plants, and quite often Gonocormus groves are washed away by typhoon waters. All this causes its population and those of other biologically closely related fern species [Mecodium wrightii (Bosch) Copel. and Pleurosoriopsis makinoi Maxim. ex Makino) Fomin] to diminish to bring them to the brink of disappearance from the flora of not only Primorye, but all of Russia as well.
Signs of affiliation to ancient floras may also be noted in Pyrrosia petiolosa (Christ et Baroni) Ching, another fern growing in Primorye. Its range encompasses Korea, Japan, the Russian Far East (Primorye and Amur Region). It occurs preferentially on cliffs. Unlike the Gonocormus, Pyrrosia is adapted to life in more arid conditions. Its petiole and leaf back sideare densely covered with stellar hairs, particularly on young growing leaves. Due to these hairs, the leaves reflect sunrays well to decrease evaporation from their surface. Besides, Pyrrosia leaf plates are arranged almost parallel to the soil surface to significantly lessen the sunray incidence angle and plate heating.
Pyrrosia rhizome is creeping, superficial and poorly adapted to cliff conditions. Logically, one could assume that in ancient times this fern was also an epiphyte, but of a different type than the dwarf Gonocormus. In frond and rhizome structure, Pyrrosia resembles cow epiphytes, which nowadays occur in the upper and middle sections of trunks and on tree branches of subtropical and tropical humid forests. At present, Pyrrosia petilosa is a rare species, whose populations and distribution ranges are gradually decreasing. For this reason, it was entered in the Red Book of the USSR (1984) and in the regional list of rare plants (Kharkevich, Kachura, 1981).
Polystichum craspedosorum (Maxim.) Diels. Diels. Is yet another rare fern species occurring in Primorye and southern Khabarovsk Territory. It is a short (up to 25 cm) plant with rosettes of leaves that winter in green state. The species is interesting in that its lancet-linear pennidissected leaves often end with a proliferating bud, which when it touches the soil gives rise to a new plant. The same viviparity is also characteristic of Camptosorus sibiricus Rupr., which may occur on cliffs and large rocks not only in the Russian Far East, but in Eastern Siberia, Mongolia and the countries of East Asia as well.
Above we spoke of terrestrial ferns; yet, Primorye flora is also represented by aqueous plant, among which there is a single fern, Salvinia natans (L.) All. Species of this genus are familiar to aquariumists: one can frequently observe in aquarium water surface American tropical species of this fern. Salvinia are plants adapted to life in water. They have no roots, and suck in nutritive substances using their water-submerged leaves dissected into narrow lobes and resembling their roots in appearance. Other types of floating leaves in Salvinia contain air cavities inside that do not allow leaves to submerge in water. Besides, the leaf upper side has suckers and hairs that prevent moistening to thereby ensure breathing and photosynthesis. Unlike terrestrial ferns, which are perennial plants, the floating Salvinia is an annual. It may occur in various (preferentially standing) water bodies of Primorye and the Amur Region, and also in a number of other areas in and beyond Russia.
Numerous ferns present interest not only to botanists as species that formed in past epochs, but also as food, commercial, decorative and medicinal plants. For instance, it has been known long ago that Pteridium aquilinum possesses a whole series of properties beneficial to man. It is a valuable tanner, and the high potassium content in its ash allows using it to obtain potash essential in manufacturing decorative glass. There is evidence in the literature (Shreter, Karnishina, 1975) indicating the possibility of utilizing Pteridium aquilinum as a medicinal plant. However, it more familiar as a food species, whose young leaves are used in food most often. Again, its dried and ground rhizomes were used in the 19th century in the Canaries, New Zealand, America and Australia to bake bread.
Other ferns growing in Primorye, e.g. the Matteucia struthiopteris (L.) Torado, may also be used as food plants. In Canada and some American States, this species is a traditional spring food of American Indians. Its leaves contain no harmful substances and man by used without preliminary treatment to cook various dishes.
Numerous Russian Far Eastern fern species have a special appearance due to their petiole color and length, dissection character and leaf form and size, and this allows to assign them to decorative-leaf plants. For example, the dark, almost black, brilliant petiole and azure semi-round plate of Adiantum pedatum L. place it among the most beautiful plants of Russian Far Eastern forests.
Various wild fern species have long been used as decorative plants. In accord with materials summarized by M. A. Skripka (1970), about 400 fern species were cultivated in gardens, greenhouses and hothouses of European Russia in the early 19th century, including also seventeen species occurring in the Russian Far East. However, they were brought from Japan, Canada, and North America. Today, too, numerous wild fern species are grown as decorative plants both in Russia and abroad.
An analysis of our over twenty-year-long study of Primorye ferns in the collection of the Botanical Garden-Institute, F. E. Branch, Russian Academy of Sciences (Khrapko, 1989, 1996) showed many of them to be promising got use in culture. You can always find a suitable fern species to decorate any park or garden corner. Many of them feel themselves well in shaded sites, where other plants cannot be planted for lack of light. Some ferns endure full illumination pretty well, and may be planted in groups and individually against grass background. Fern lace foliage looks especially striking in combination with uneven surface of large stones. Miniature cliff ferns serve as good decorations for any hill or rocky garden.
Russian Far Eastern ferns can suitably be grown as decorative plants not only in open soil. The evergreen fern species available in Primorye flora, e.g. the Polypodium sibiricum Sipl. retain their leaves and consequently their decorative appearance throughout the year. Such species may expand the assortment of decorative shade-enduring plants used in interior landscaping.
Significantly, today irrational use of natural thickets of food ferns and increased man-made impact on vegetation cover have resulted in decrease and gradual lessening of the areas of numerous representatives of this ancient group of plants. Already today, twenty-three fern species (Kharkevich, Kachura, 1981) have been entered in the list of rare plants from the Russian Far East, and Osmunda Claytoni and Pyrrosia ligula in the Red Book of the USSR. A more detailed study of this group of plants shows that the list of rare representatives may be continued.
To use the resources of Russia’s Far Eastern ferns more rationally and to retain their gene pool, one should now the specificity of their biology, ecology and multiplication. The most complete evidence for solving such issues may be obtained by summarizing observations of plants both in natural habitats and in culture. The Botanical Garden-Institute, Far East Branch, Russian Academy of Sciences, has been conducting such investigations for over twenty years now. Over the years, fifty-five Far Eastern fern species have been tested in culture, and at present our fern collection numbers forty species, seven of which are rare and disappearing plants.
The study of ferns has resulted in a system of measures for protecting the gene pool of rare and decreasing species of Russian Far Eastern ferns, their landscaping assortment, and recommendations for using them in landscaping and multiplication. All these and other materials may be passed over to interested persons or organizations.
Please write to: Olga V. Khrapko, Botanical Garden-Institute, F. E. Branch, Russian Academy of Sciences, 142 Makovsky Street, Vladivostok 690024, Russia.
The author sincerely thanks M. N. Abankina and A. I. Belikov for the photographs and slides
O. KHRAPKO, D. Sc. (Biology), Head, Laboratory
of Russian Far Eastern Flora, Botanical Garden, F. E. Branch, Russian Academy