ECOLOGY OF PTERIDOPHYTES

Most of the pteridophytes (ferns and fern-allies) show their luxuriant and vigorous growth

during the rainy season particularly in the hilly regions usually above 1400 m altitude.

With the commencement of monsoon about mid June, the ferns and fern-allies start

growing vigourously and luxuriantly. This is due to the fact that there has been a

prolonged dormancy awaiting the onset of rains. Because of high humidity in the

atmosphere during July- mid September, there is a prolific growth and development of

ferns and fern-allies all round on all possible habitats. This is particularly true for

epiphytic and lithophytic ferns, which cloth the tree trunks, branches, boulders and stony

walls with thickly clad felts of mosses and leafy liverworts and retain a considerable

amount of moisture and thus providing coverage and protection to the growing rhizomes.

Apart from these, there are number of hardy terrestrial species that grow throughout the

year. Some species also show a marked differences in altitudinal distribution. On the basis

of their broad hahitats, the pteridophytic flora of the study area can briefly be divided into

following ecological groups.

1. EPIPHYTES

Epiphytic ferns generally prefer to grow on moist and shady tree trunks, branches,

tree tops and large shrubs both in dense and partially and completely open forests. The

composition and frequency of these epiphytic ferns vary considerably depending upon the

altitudes, climatic conditions and nature of forests i.e. nature of bark and shade or open

nature of canopy. Usually conifers do not appear to favour the growth of any epiphytic

pteridophytes probably due to resinous bark. But it has been observed at places where

sufficient moisture and shade are available, there is a substantial growth of epiphytic

mosses and ferns.

Epiphyic ferns like Pyrrosia costata (Wall. ex Presl) Tag. & Iwats., P. flocculosa

(D.Don) Ching, P. porosa (Presl) Hovenkamp, Microsorum membranaceum (D.Don)

Ching, Lepisorus nudus (Hook.) Ching grow on the tree trunks, branches in forested and

open places of several trees especially on Mangifera indica L., Toona ciliata M. Roem.,

Sapium insigne (Royle) Benth.& Hook. f., Quercus glauca Thunb., Q. leucotrichophora

A. Camus, Syzygium cumini (L.) Skeels, Pyrus pashia Buch.-Ham. ex D.Don etc. All

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these species also grow equally as lithophytes on well moist and shaded localities

between 800 and 1200 m altitudes. While those growing above 1,200 to 2,356 m altitudes

are among the majority of epiphytic ferns such as Loxogramma involuta (D.Don) Presl, L.

porcata Price, Arthromeris lehmanii (Mett.) Ching, A. wallichiana (Spreng.) Ching,

Drynaria mollis Bedd., D. propinqua (Wall. ex Mett.) J. Sm., Lepisorus mehrae Fras.-

Jenk., L. scolopendrium Phymatopteris oxyloba (Wall. ex Kunze) Pich. Serm.,

Polypodiatrum argutum (Wall. ex Hook.) Ching, Polypodiodes amoena (Wall. ex Mett.)

Ching, P. lachnopus (Wall. ex Hook.) Ching, P. microrhzoma (Clarke ex Baker) Ching,

Vittaria flexuosa Fée, Asplenium ensiforme Wall. ex Hook.& Grev., A. laciniatum D.Don,

Elaphoglossum marginatum (Wall. ex Fée) Moore, Oleandra wallichii (Hook.) C.Presl,

Araiostegia pulchra (D.Don)Copel. etc. These epiphytic ferns tend to form a dominant

and conspicuous epiphytic vegetation on the tree trunks and branches of several species

together with large shrubs such as Lyonia ovalifolia (Wall.) Drude, Quercus

leucotrichophora A. Camus, Rhododendron arboreum Smith, Symplocos chinensis

(Lour.) Druce, Viburnum cotinifolium D.Don etc. All these ferns also grow lithophytically

as facultative epiphytes except Drynaria mollis Bedd., Oleandra wallichii (Hook.)C.Presl,

Elaphoglossum marginatum (Wall. ex Fee)T.Moore and Goniophlebium argutum (Wall.

ex Hoo.)J.Sm., which are obligate epiphytes and can survive without proper hosts. It is

interesting to note that Oleandra wallichii (Hook.) C. Presl, and Elaphoglossum

marginatum (Wall. ex Fée) T.Moore have been recorded exclusively on R. arboretum

Smith, while D. mollis Bedd and G. argutum (Wall. ex Hook.) Ching were recorded on

Q. leucotrichophora A. Camus in addition to R. arboreum Smith It is interesting to note

that among the epiphytes, polypodiaceous members are the commonest and most

dominant in the present study and as well as throughout the Himalayan ranges.

2. LITHOPHYTES

This group of ferns generally grow firmly attached to rocks with their creeping

rhizomes. Such species also show xerophytic characters which help them to overcome

unfavourable conditions. Some of the common lithophytic ferns which grow on rock

surfaces, boulders and stone walls are Adiantum incisum Forssk., A. philippense L.,

Cheilanthes doniana Fras.-Jenk. & Khullar, C. dubia Hope, C. leptolepis Fras.-Jenk., C.

rufa D.Don, Botrychium lanuginosum Wall. ex Hook. & Grev., Pteris aspericaulis Wall.

ex J.Agardh, Trichomanes latealatum (v.d.Bosch.)Christ, Hymenophyllum exsertum

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(Wall. ex Hook.) Bedd., Hypodematium crenulatum (Forssk.) Kuhn, Asplenium

dalhousiae Hook., A. filipes, P. mehrae Fras.-Jenk. & Khullar, P. nepalensis

(Spreng.)C.Chr., P. thomsonii (Hook.f.) Bedd., Tectaria macrodonta (J.Sm.) C.Chr.,

Elaphoglossum marginatum, Nephrolepis cordifolia (L.)Presl, Araiostegia pulchra

(D.Don)Copel., Leucostegia immersa Wall. ex C.Presl. Under dripping water on rocks

and walls Adiantum capillus-veneris L. flourishes extremely well and grows over large

areas forming big colonies. Besides, majority of epiphytioc ferns also tend to grow as

lithophytes in moist and well shaded localities.

Among the fern-allies, Selaginella species usually prefer to grow on rocks and

boulders such as S. chrysocaulos (Hook. & Grev.) Spring, S. involvens (Sw.) Spring, S.

pallidissima Spring and S. subdiaphana (Wall. ex Hook. & Grev.) Spring. Among these

species, S. involves grows as foot epiphyte also. All these specis are common throughout

the study area and they grow extensively forming mats on rocks and walls in the forest,

forest margin, waysides and roadsides. They become particularly conspicuous during

rainy and autumn seasons.

3. TERRESTRIAL FERNS

A large number of ferns of the study area consists of terrestrial ones. They generally

grow in open places, humus rich forest floor, forest margin, waysides and roadsides

forming a conspicuous vegetation. Some common terrestrial ferns are: Dicranopteris

linearis (Burm.f.) Underw., Pteris aspericaulis Wall. ex J.Agardh, P. biaurita L., P.

cretica L., P. excelsa Gaud., P. subquinata Wall. ex Agardh, P. wallichiana Agardh,, P.

vittata L., Onychium crypogrammoides Christ, O. japonicum (Thunb.) Kunze., Pteridium

revolutum (Blume) Nakai, Adiantum edgeworthii Hook., A. venustum D.Don,

Coniogramme pubescens Hieron., Athyrium schimperi Moug. ex Fée subsp. biserrulatum

(Christ) Fras.-Jenk., A. pectinatum (Wall. ex Mett.) Moore, Polystichum discretum

(D.Don) J.Sm., P. squarrosum (D.Don) Fée, Dryopteris chrysocoma (Christ) C.Chr., D.

cochleata Buch.-Ham. ex D.Don) C.Chr., Diplazium spectabile (Wall. ex Mett.) Ching,

Hypolepis polypodioides (Blume)Hook. Several lithophytic species may also tend to grow

terrestrially on forest floor, forest margin, open places, roadsides and waysides and the

common ones are the members of Athyrium, Dryopteris, Polystichum, Pteris, Diplazium

etc.

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4. AQUATIC AND MARSHY FERNS

True aquatic ferns have not been observed in the study area. However ferns growing

in wet and muddy places are considered as marshy ferns which commonly grow along the

banks of perennial streams, water channels and water falls etc. leading to form a

conspicuous and prominent vegetation. They include Dennstaedtia appendiculata (Wall.

ex Hook.)J.Sm., Diplazium esculentum (Retz.) Sw., D. laxifrons Rosent., D.maximum

(D.Don) C.Chr., D. spectabile (Wall. ex Mett.) Ching, D. squamigerum (Mett.)Matsum.

Besides, Equisetum diffusum D.Don grows profusely in marshy and wet places covering

considerable areas and form big colonies.

5. RAVINE FERNS

Ferns growing in ravines require more humidity, moisture and dampness than the

ferns growing in open places. Therefore they usually prefer to grow in the ravines

forming large colonies near perennial water courses, which provide them suitable habitats

for their growth and development throughout the year. Such ferns commonly growing in

the ravines are: Diplazium laxifrons Rosent., D. maximum (D.Don) C.Chr., D. spectabile

(Wall. ex Mett.) Ching, Thelypteris auriculata (J. Sm.) K.Iwats., Thelypteris erubescens

(Wall. ex Hook.) Ching, T. mollissima Fisch. ex Kunze) N.Thapa, T. nudata

(Roxb.)C.V.Morton, T. phegopteris (L.) Slossom, T. pyrrhorhachis (Kunze) C.M.Kuo,

Coniogramme pubescens Hieron., Woodwardia unigemmata (Makino) Nakai, Cyrtomium

caryotideum (Wall. ex Hook. & Grev.) Presl, Polystichum nepalense (Spreng.) Presl and

several others.

6. THICKET FORMING SPECIES

Three species of ferns has been identified in the present study area which are

somewhat hardy and robust and grow on more open exposed rocky and gravelly

situations. They are usually exposed to a wide range of climatic variations such as high

and low wind velocities, marked temperature fluctuations and varied amount of moisture

content i.e. Pteridium revolutum (Blume) Nakai forms huge colonies in recently exposed

ridges, on forest floor, forest edges, grasslands, orchards, on highly rigorously exposed,

dry and open situations. Rhizomes are deeply buried under the soil and creep long

distances with wide branching. The fronds form tangled mass and thus do not allow

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anything to grow. Second one is Dicranopteris linearis (Burm.f.) Underw. which also

tends to form large and huge colonies or patches on exposed and open rocky localities due

to its creeping rhizomes and covers large areas forming thickets in grasslands and forest

margin and chir-pine forests. This species grows almost in pure formation and sometimes

climbs to a considerable height on neighbouring bushes.Third one is Pteris wallichian

J.Agardh which is very tall, hardy and robust species and shows its vigorous growth and

development in the study area and forms large colonies along open as well as wet places,

field border, road banks and forest margin covering considerably a large areas due to its

long-creeping rhizomes and thus has become the most successful species.

7. SEASONAL ASPECTS

Climatic variations and fluctuations greatly influence the growth and development of

ferns and fern-allies. The ferns of the study area like other parts of Himalayan regions

also exhibit a marked seasonality among themselves. It has been noticed that most of the

species grow during rainy season between mid June to mid September. With the advent of

first showers of rain and early heat of summer (April to June), almost all the species put

forth new fronds which grow vigorously and become fertile during August to September.

These species gradually cover different habitats till early October.

With the beginning of winter season (November to March), all the epiphytic and

lithophytic ferns undergo dormant period after shedding quickly their fronds due to

prevailing unfavourable and adverse climatic conditions. During this period, only

shrivelled up or enrolled dry, yellowish fronds of certain epiphytic and lithophytic species

like Loxogramme involuta (D.Don) Presl, Asplenium yoshinage subsp. indicum (Sledge)

Fras.-Jenk., Pyrrosia flocculosa (D.Don) Ching, P. porosa (C.Presl) Hovenkamp, Vittaria

flexuosa Fée, Lepisorus nudus (Hook.) Ching etc. can be seen. The aerial parts die off

completely or partially giving sudden disappearance of these species. But the undergrown

and creeping rhizomes covered by leafy bases, scales and hairs help them to overcome

unfavourable conditions during winter season and become active with the commencement

of spring season. However, some species of hardy ferns like Polystichum discretum (D.

Don) J.Sm., P. squarrosum (D.Don) Fée, Cyrtomium caryotideum (Wall. ex Hook. &

Grev.) C. Presl, Dryopteris chrysocoma (Christ) C.Chr., D. cochleata (Buch.-Ham. ex D.

Don) C.Chr., D. redactopinnata S.K.Basu & Panigrahi, D. wallichiana (Spreng.) Hyl.,

Pteridium revolutum (Blume) Nakai, Diplazium esculentum (Retz.) Sw., D. laxifrons

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Rosent., D. maximum (D.Don)C.Chr., Hypodematium crenulatum (Forssk.) Kuhn,

Hypolepis polypodioides (Blume) Hook., Adiantum capillus-veneris L., A. venustum

D.Don, Tectaria macrodonta (J.Sm.) C. Chr., Pteris aspericaulis Wall. ex J. Agardh, P.

excelsa Gaud., P. vittata L., P. wallichiana Agardh, Woodwardia unigemmata (Makino)

Nakai etc. remain green throughout the year, although they produce new fronds only after

the spring.

During winter months, the aerial parts of almost all terrestrial species are killed

completely or partially by snow and frost above 1,500 m altitude, but species growing on

walls and other protected situations remain green throughout the winter season.With the

advent of spring together with summer heat and pre-monsoon showers, the area resumes

its dense growth of vegetation throughout the area.

8. ASSESSMENT OF RARE AND ENDANGERED SPECIES

Like the other parts of world, the flora of the Himalayan region including the present

study area is also under direct biotic pressure due to selective removal as well as habitat

clearance for cultivation. The habitat fragmentation particularly in areas where most of

the plants grow has probably caused their being rare and endangered. The depletion and

disappearance of these plants have largely been due to road construction, dam building

and establishment of industries on a large scale in recent past. The bulk of collections of

medicinal and useful plants has also played an vital role in the depletion and

disappearance of plants. A large area once occupied by dense forests have been converted

into grazing and scrub lands owing to destruction of natural habitats on exponential scale,

indiscriminate deforestation and over grazing leading to disturbed ecological balance.

Besides floods, soil erosion and landslides also convert considerable areas into stony

deserts. Thus the destruction of natural habitat by any one factor results in entirely

different habitat invaded by other groups of plants and making the conditions

unfavourable and unsuitable for their existence and survival. With the result, some plants

have become threatened and endangered, while the rare ones are on the verge of

depletion. If these conditions continue to operate for some more years, these threatened,

endangered and rare species are bound to disappear from this area in near future.

Based on field observations in the study area indicate that majority of species fall in

the rare and endangered categories. All these plants have been collected only once or

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twice consisting of small population in nature and grow in a very specialised habitats in

miserable conditions due habitat fragmentations and direct biotic disturbances. Among

them, a few species listed below. They are: Lycopodium annotinum L., Botrychium

lunularia (L.)Sw., B. ternatum (Thunb.)Sw., Osmunda japonica Thunb., Ctenopteris

subfalcata (Blume) Kunze, Loxogramme chinensis Ching, Arthromeris lehmanii (Mett.)

Ching, Lepisorus clathratus (C.B.Clarke)Ching, Cheilanthes anceps Blanf., C.dubia

C.Hope, Notholaena marantae (L.) Desv., Pteris puberula Ching, Adiantum myriosorum

Baker, Vittaria taenophylla Copel., Trichomanes campanulatum Roxb., Lindsaea odorata

Roxb., Asplenium adiantum-nigrum L., A. aitchinsonii Fras.-Jenk. & Reichst., A.

capillipes Makino, A.khullarii Reichst., Rasbach & Fras.-Jenk., Metteucia intermedia

C.Chr., Woodsia alpina (Bolton)S.F.Gray, Athyrium distans (D.Don) Moore, A.

flabellulatum (C.B.Clarke) Tardieu, Cornopteris quadripinnatifida M.Kato, Deparia

subsimilis (Christ)Fras.-Jenk., Diplazium spectabile (Wall. ex Mett.) Ching, D.

squamigerum (Mett.) Matsum, Gymnocarpim fedtschenkoanum Pojark, Peranema

cyatheoides D.Don, Cyrtomium caryotideum (Wall. ex Hook. & Grev.) C.Presl, C.

macrophyllum(Makino)Tagrawa, Dryopteris redactopinnata S.K.Basu & Panigrahi, D.

subimpressa Loyal, Polystichum mehrae Fras.-Jenk.& Khullar, P. stimulans (Kunze ex

Mett.) Bedd., Elaphoglossum marginantum (Wall. ex Fée) Moore and several other.

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Botrychium lanuginosum

Arthromeris wallichiana

Drynaria mollis

Dicranopteris linearis

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Goniophlebium argutum

Lepisorus scolopendrium

Phymatopteris oxyloba

Phymatopteris stewartii

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Polypodiodes microrhizoma

Cheilanthes leptolepis

Onychium cryptogrammoides

Hypolepis polypodioides

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Pteris biaurita

Pteris cretica

Pteris puberula

Pteris vittata

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Pteris wallichiana

Adiantum venustum

Coniogramme intermedia

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Vittaria flexuosa

Dennstaedtia appendiculata

Asplenium filipes

Athyrium fimbriatum

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Thelypteris erubescens

Thelypteris nudata

Thelypteris pyrrhorhachis

Cyrtomium caryotideum

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Dryopteris barbigera

Dryopteris chrysocoma

Dryopteris redactopinnata

Dryopteris wallichiana

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Polystichum nepalense

Polystichum stimulans

Araiostegia pulchra

Woodwardia unigemmata

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Author studying ferns in the fieldEstelar