Pteridophytes

(1) The diversity of pteridophytes in China

There are between 10,000～12,000 species of pteridophytes in the world. Of these, between 2, 200-2, 600 species occur in China, and constitute 22% of the world total. Because of China's large territory, and complex and diversified natural environment, except for a few tropical families and genera, the number of Chinese pteridophytic families and genera constitutes about 95% of the world total, i. e., pteridophyte diversity in China is high.

Some species are important for the study of evolution and systematics and are widely distributed in China, e.g., the primitive taxa Psilotum nudum and Christensenia of Psilopsida Some genera, such as Cystoathyrium and Sinopteris, with small distributions, are endemic to China. Their discovery has significance for the study of generic and family evolutionary relationships. Adiantum reniforme, which was discovered along the banks of the Yangtze River, Eastern Sichuan, was originally identified from Madeira in the Atlantic Ocean. The occurrence of a Chinese variety, Adiantum reniforme var. sinense, provides good evidence for a disjunct distribution and relationships between Chinese and African pteridophytes. Sorolepidium glaciale, which can live in alpine frigid deserts at an altitude of 4350m, is an important taxa for studies of the relationship between pteridophyte morphology and ecology. Struthiopteris eburnea, which can be found only on the rocky cliffs of Southwestern China and Hunan Province, typically grows on calcareous, limestone and soils.

According to incomplete statistics, between 500-600 species of pteridophyte are endemic to China, accounting for 25% of the total species list. China's endemic genera and representative species are shown in Table 1.

Table 1 The endemic genera and representative species of pteridophytes in china

Representative species of endemic genera	Geographical distribution
Cyrtogonellum fraxinellum	Sichuan, Yunnan, Guizhou, Guangxi
Cystoathyrium chinense	Sichuan
Phanerophlebiopsis tsiangiana	Guizhou
Sinopteris grevelleoides	Sichuan, Yunnan
Sorolepidium glaciale	Yunnan
Trichoneuron microlepioides	Yunnan

(2) The status of China's threatened and endangered pteridophytes

Some new species of pteridophyte are continuously being discovered in botanical surveys of different parts of China. At the same time, however, some species have either disappeared or are endangered due to the environmental changes and human activities (Table 2). Except for the endemic and endangered species mentioned above (Tables 1 and 2), there are some species whose distributions, though not confined to China, are locally limited, such as Platycerium wallichii. This plant lives only along the Yinjiang River near the border between China and Burma. Marsilea aegyptica is found only in some local water bodies in Xinjiang. These species are highly endangered if not well protected, because of small population sizes and restricted distributions. There are many such endangered species and it is estimated that they account for about 30% of the total pteridophyte flora of China. The most important 101 species are listed here (Table 3)

Table 2 Extinct and endangered Chinese pteridophytes

Species	Extinct	Endangered
Isoetes sinensis		+
Trichoneuron microlepioides	+
Cystoathyrium chinense		+
Cyrtomium bemionitis	+

Table 3 Some important rare and endangered pteridophytes in china

Acrostichaceae	Hemionitis arifolia
Acrostichum speciosum	Neottopteris phyllitidis
Adiantaceae	Phyllitis japonica
Adiantum fengianum	Sinephopteris delavayi
Adiantum reniforme var. sinense	Athyriaceae
Adiantum sinicum	Cystoathyrium chinense
Angionpteridaceae	Bolbitiaceae
Angiopteris sparsisora	Egenolfia sinensis
Archangiopteris bipinnata	Blechnaceae
Archangiopteris henryi	Brainea insignis
Aspidiaceae	Botrychiaceae
Ctenitopsis sagenioides	Botrychium decurrens
Hemigramma decurrens	Cheiropleuriaceae
Lastreopsis hainanensis	Cheiropleuria bicuspis
Pleocnemia winitii	Christenseniaceae
Pteridrys cnemidaria	Christensenia assamica
Tectaria variabilis	Cyathyaceae
Aspleniaceae	Alsophila contaminans
Boniniella cardiophylla	Alsophila fenicis
Ceterachopsis dalhousiae	Alsophila loheri
Ceterach officinarum Diploblechnum fraseri	Alsophila spinulosa Oleandraceae
Sphaeropteris hainanensis	Oleandra hainanensis
Sphaeropteris lepifera	Ophioglossaceae
Davalliaceae	Ophioderma pendulum
Davallia stenolepis	Ophioglossum thermale
Dipteridaceae	Plagiogyriaceae
Dipteris conjugata	Plagiogyria assurgens
Drynariaceae	Platyceriaceae
Drynaria rigidula	Platycerium wallichii
Photinopteris speciosa	Pleurosoriopsidaceae
Pseudodrynaria coronans	Pleurosoriopsis makinoi
Dryopteridaceae	Polypodiaceae
Arachniodes hasseltii	Belvisia annanensis
Cyrtomium bemionitis	Christioprteris tricuspis
Cyrtomium nephrolepioides	Drymoglossum piloselloides
Dryopteris cyclopeltiformis	Schellolepis subauriculatum
Dryopteris tokyoensis	Leptochilus cordatus
Polystichum alcicorne	Lepisorus loriformis
Sorolepidium glaciale	Neocheiropteris palmatopedata
Grammitidaceae	Phymatoddes longissima
Calymmodon cuculatum	Phymatopsis triloba
Grammitis hirtella	Polypodium vulgare
Prosaptia urceolaris	Pyrrosia hastata
Scleroglossum pusillum	Psilotaceae
Gymnogrammitidaceae	Psilotum nudum
Gymnogrammitis dareiformis	Pteridaceae
Helminthostachyaceae	Pteris subsimplex
Helminthostachys zeylanica	Pteris tricolor
Hemionitidaceae	Pteris tripartita
Anogramma leptophylla	Pteridiaceae
Coniogramme petelotii	Paesia taiwanensis
Hemenophyllaceae	Schizaeaceae
Cephalomanes laciniatum	Schizaea digitata
Crepidopteris humilis	Sinopteridaceae
Meringium acanthoides	Aleuritopteris chrysophylla
Nesopteris grandis	Aleuritopteris squamosa
Nesopteris thysanostoma	Cheilanthes belangeri
Isoeteaceae	Cryptogramma brunoniana
Isoetes hypsophila	Doryopteris ludens
Isoetes japonica	Sinopteris albofusca
Isoetes sinensis	Sinopteris grevilleoides
Isoetes taiwanensis	Stenochlaenaceae
Lomariopsidaceae	Stenochlaena hainanensis
Lomagramma grossoserrata	Stenochlaena palustris
Lomariopsis spectabilis	Thelypteridaceae
Marattiaceae	Trichoneuron microlepioides
Marattia pelucida Marsileaceae	Cyclosorus nanpingensis Woodsiaceae
Marsilea aegyptica	Cheilanthopsis indusiosa

The reasons why pteridophytes are endangered are as follows：

a. Deforestation, resulting in a reduction of atmospheric moisture and a lowering of the groundwater table changes the original habitats. This will affect the survival and reproduction of plant species. For example, Cystoathyrium chinense was collected in 1963 from forest areas at 2, 450m above sea level at Tuanniuping, Erlangshan, Sichuan Province. In 1984, that forest had disappeared, the climate had become drier, and only one Individual plant of this species was found in the bushes.

b. Some species are extinct due to industrial development and agricultural constructions, e. g., Isoetes sinense and Adiantum reniforme var. sinense.

c. Some species have been almost lost because of their propagation by people for their medical and ornamental uses, but without concern for their protection, such as Adiantum reniforme var. sinense and Platycerium wallichii.

d. In tourist areas, some small, rare, plant species, like Othioglasum tkermale, have suffered from severe trampling.

(3) Enhancing the protection of Pteridophytes

Pteridophytes have a close relationship with people. Many species have been used in Chinese traditional medicine, and they constitute about 10% of the total species numbers. For example, Cyrtomium fortunei, Lygodium japonicum and Davallia barometz strengthen the bone and kidney; Dryopteris crussirhizoma and Pyrrosia lingua and others can treat tracheitis and nephritis. In addition, Cibotium barometz is good for the liver and kidney and has the function of strengthening the waist and knee. In recent years, this species has developed a great commercial potential, over one hundred tonnes of its rhizomes being exported each year. Although this species is widespread in China, it must be protected by limitations on exports. Most pteridophytes are shade plants, With sturdy and thick leaves, suitable for use as decorative plants. The fiddleheads of some species such as Callipteris esculenta, Pteridium aquilinum var. latiusculum and Matteuccia struthiopteris are edible. There is a blue-green alga, Anabaena symbiosis, under the leaves of Azalla imbricate which can fix atmospheric nitrogen. It is a valuable green manure in rice fields. Pteridophytes and other green plants jointly create the necessary environment for human life on earth. It is our responsibility to protect them. First, we have to set up special protected areas for rare and endangered species, for example, the Nature Reserve for Tree Ferns of Chishui, Guizhou Province. Second, set up experimental gardens for introduction into areas similar to the original environments of some species, like Adiantum reinforce var. sinense, where they are threatened by construction projects in the Three Gorges. Third, enhance the education of local people to recognize the importance of plant biodiversity, and forbid unlimited collection of some economic pteridophyte species.