Highland vegetation and flora of Van Ban District, Lao Cai province in northern Viet Nam Текст научной статьи по специальности «Биологические науки»

УДК582.594(597)

L.V. Averyanov Phan Ke Loc Nguyen Tien Hiep Do Tien Doan

Л.В. Аверьянов Фан Ке Лок Нгуен Тьен Хиеп До Тиен Доан

HIGHLAND VEGETATION AND FLORA OF VAN BAN DISTRICT,

LAO CAI PROVINCE IN NORTHERN VIET NAM ФЛОРА И РАСТИТЕЛЬНОСТЬ ВЫСОКОГОРИЙ ПРОВИНЦИИ ЛАО КАЙ СЕВЕРНОГО ВЬЕТНАМА

A short survey of the flora and vegetation of Lang Cung Mountains located in Van Ban District, Lao Cai Province in northern Viet Nam is compiled on the base of original data obtained from field work conducted during 2001-2002. Description of main types of plant communities and brief analysis of the flora are based on model plot descriptions and extensive herbarium collections. Closed evergreen tropical monsoon (seasonal) forest is the main vegetation type in the studied area. This formation is subdivided into lowland, submontane, lower montane and upper montane forests, which are described in detail. The characteristics of vegetation and taxonomic composition of the studied flora are typical for southeastern extension of montane uplands of Sikang-Yunnan floristic province in the limits of Hoang Lien Son Range. This flora represents a derivative of ancient Tertiary flora, which includes a great number of archaic genera common to Europe and East Asia during Upper Cretaceous and Lower Tertiary. In reference to its origin and composition, this flora represents unique relictual formation, which may serve as a model for the study of extinct floras that were once widely distributed in the Northern Hemisphere during the Tertiary.

Introduction

The northwestern part of Viet Nam is a mountainous area with a number of high ranges coming from northwest to southeastern direction. The largest mountain formation of this region is the Hoang Lien Son Range. It represents the southeastern extension of the Himalayas, which extends from Yunnan into northern Viet Nam. This range forms in northwestern part of Viet Nam a large, clear, outlined, and distinct mountainous region, which appears as a vast area of uplands, extending above 16002000 m with a number of peaks reaching 2500-3000 m a.s.l. The highest peaks in mainland Southeast Asia, such as Fan Si Pan (3143 m) and Lang Cung (2913 m), are located here. Most of highest mountain formations of Hoang Lien Son Range consist of huge granite or quartzite intrusions of late Mesozoic age.

The highland area associated with Hoang Lien Son Range is outlined in modern biogeography as the southeastern part of Sikang-Yunnan floristic province of Holarctic floristic kingdom (Takhtajan, 1978, 1986; Averyanov, et al., 2003). This region lies on the border of Holarctic and Paleotropic realms and represents a very important boundary area with numerous tropical, subtropical, and temperate floristic connections, studies

of which explain the many aspects of historical formation and development of modern floras of Southeast Asia and Indochinese Peninsula. At the same time local endemism in Sikang-Yunnan floristic province is very high (Averyanov, 2002a, 2002b; Averyanov, et al., 2002, 2003), which makes this flora one of the richest and specific indigenous floras of mainland Asia. Investigations on the flora of Sikang-Yunnan floristic province represent outstanding fundamental scientific interest. Nevertheless, it is very far from being a complete, adoptable and reasonable inventory. Few acceptable botanical surveys exist for the Vietnamese portion of the Sikang-Yunnan floristic province. The meager published works on the flora of Fan Si Pan Mountains are still being used for all the vast territory of Hoang Lien Son Range (Nguyen Nghia Thin, Harder, 1996; Nguyen Nghia Thin, 1998; Nguyen Nghia Thin, Nguyen Thi Thoi, 1998). Some fragments of basic botanical data could be found in general fundamental taxonomic publications on the flora of Vietnam, such as “Flore Generale de l’Indochine” (ed. M.H. Lecomte, H. Humbert, 1907-1951), “Flore du Cambodge, du Laos et du Viet-Nam” (ed. A. Aubreville, J.F. Leroy, Ph. Morat, 1960-1997), “An illustrated flora of South Viet-Nam” and “An illustrated flora of Vietnam” (Pham Hoang Ho, 1970-1972; 1991-1993; 1999-2000), “Vascular plant synopsis of Vietnamese flora” (ed. L. Averyanov et al., 1990, 1996) and in a number of recent floristic and taxonomical papers and monographs (Seidenfaden, 1975, 1992; Averyanov, 1988, 1989, 1990a,b, 1994, 1998, 1999a,c, 2000a,b, 2002c-e; Vu Van Dung, 1996; Nguyen Nghia Thin, 1997, 1999; Averyanov and Averyanova, 2000, 2003; Averyanov, Phan Ke Loc, 2002; Averyanov et al., 2002, 2003; Vu Ngoc Long, Averyanov, 2002 and some others) 1. However, the vast highland area of Hoang Lien Son Range with its very rich endemic indigenous flora and unique montane types of vegetation remains up to now botanically unexplored and undocumented.

At the same time, it is very important to emphasize that deforestation, degradation, and destruction of natural habitats are presently widespread all over wide areas of the Hoang Lien Son Range. In this critical situation, urgent botanical investigations in this region are very important for providing sound scientific data for the protection of the forests and conservation of still remaining primary unique plant communities, that have worldwide significance as centers of outstanding plant diversity.

The southern part of Van Ban District along border of Lao Cai and Yen Bai Provinces was selected as the study area for a number of reasons. First, it still has relatively large, pristine, highland mountain forests, which represent typical mountain vegetation of the southern part of Hoang Lien Son Range. Second, it is a very important refugium for numerous indigenous animal species. Third, there is a proposal to designate the area as a very important protected nature reserve in Viet Nam.

Materials and methods

The general outline of original primary flora and vegetation, as well as description

1 Bibliographies of published studies of the Indochina flora have been published, each covering sequential periods oftime by Petelot (1955), Vidal (1972) and Vidal et al. (1988, 1994).

of most typical primary zonal and azonal plant communities were made at 700-2640 m elevation during field work in southern part of Van Ban District, Lao Cai Province of northern Viet Nam in September-October 2001 and in March 2002.

The description of forest structure and taxonomic composition of vegetation types and plant communities was made along landscape profiles (transects) from lowest to highest elevation starting from the lowest mountain belt where primary forests were observed. Various kinds of secondary plant formations, that represents different stages of degradation of primary plant communities (various kinds of secondary forests, secondary shrubs, secondary grasslands, weed and ruderal plant communities, etc.) were not studied and not included in this paper.

The description of vegetation was based on field observations along landscape transects and detailed descriptions of forest structure and species composition in temporary plots, selected at different elevations in most typical and representative plant communities. Selected plots varied in size from 10x10 m (for herb or cliff lithophytic plant communities) to 20x50 m (for high forest formations). The size of selected plots depended on the largest possible size of land available with rather uniform, homogeneous vegetation cover. Model plots were selected in all types of primary plant communities, which were observed along studied landscape profiles and transects.

The size of model plots commonly used for description of species composition and vegetation of forest formations was 20x40 m. For each plot were measured the geographical coordinates, elevation above sea level, slope exposure and inclination. In this work were used standard GPS receiver, altimeter, compass and topographic maps (1:50000). In each plot were briefly described features of leaf litter, main soil horizons and parent rocks. Vegetation structure was described for each distinctly observed stratum with determination of projective coverage and taxonomic composition for each storey (including herb and moss/lichens strata). Detailed descriptions of non-strata component of plant communities - epiphytic, lithophytic, climber and vine plants, as well as plants of specific life forms, such as root and canopy parasites, mycotrophic achlorophyllous herbs, etc. were provided for each model plot with determination of dominant species. Special attention in field studies was given to the orchids (Orchi-daceae) and gymnosperm species (Cupressaceae, Pinaceae, Podocarpaceae, Taxodia-ceae). Number of tree boles with their diameter for each tree strata were given forest descriptions for each plot. The diameter of the tree bole was measured at breast height about 1.5 m above the ground.

Additional important information on vegetation structure and species composition of primary plant communities in the studied area was obtained from field observations and plant collections during numerous extensive botanical explorations done on foot in the studied mountains.

The descriptions of vegetation and plant communities were entered in standard form. Each name in these descriptions were based on voucher herbarium specimens, which are housed with appropriate collecting number2 and name in Herbaria at the Institute of Ecology and Biological Resources of the National Center for Natural Science and Technology of Viet Nam (HN), Royal Botanical Gardens, Kew (K), Komarov

Botanical Institute of the Russian Academy of Sciences (LE) and Missouri Botanical Garden (MO). Flowers of the most important, rare and scientifically significant species were also collected in alcohol (in addition to herbarium material) and were deposited at HN. Photographs of typical and most significant plants of studied area were also made and copied onto CD-ROM.

Geography and geology of the studied area

Geographically and geologically, Hoang Lien Son Range and associated highland mountain areas represent the farthest SSE extension of Himalayan uplands and therefore have similar origin, structure and rock composition. The extreme southeastern portion of Hoang Lien Son Range is marked by Lang Cung mountain system. The highest peak of this system reaching 2913 m lies on the border of Lao Cai and Yen Bai Provinces. The northern branches of this mountain system that are generally north-faced slopes represent large highland area that occupies southern part of Van Ban District between 21°54’-22°01’ N latitude and 103°57’-104°22’ E longitude. This upland area extends in the region from the NWW to the SEE to about 40 km ranging in width from 6 to 18 km.

Generally, mountain systems here are composed of magmatic silicate rocks particularly granite and quartzite, which were formed as extensive intrusions of late Paleozoic and Mesozoic ages (Dovzikov et al., 1965a, b). According to our observations, large mountain formations in the studied area are also composed of solid, highly pressed, deeply metamorphosed sandstone with high amount of silicates consolidated with more or less large numerous quartzite dikes. Pure white quartzite is also a common kind of rock that comprised the highland of Van Ban District. Tertiary tectonic movements uplifted these mountain terrains up to present-day elevations and succeeding erosion processes formed the present-day characteristic rocky landscape of this highland area with very steep slopes, numerous rocky cliffs and deep narrow river canyons (Schzeglova, 1957; Fridland, 1961; Rundel, 1999; Averyanov, et al., 2003).

The remnant rocky hills and mesas comprised of eroded solid crystalline limestone of presumably late Paleozoic or early Mesozoic ages are widely observed in the lowland areas of Van Ban District outside of the study area.

Climate

A monsoon tropical climate associated with mountains is typical of Viet Nam in mountain areas higher than 1400-1500 m a.s.l. (Nguyen Khanh Van, et al., 2000). Such climate is spread across the largest mountain ranges of the northern Viet Nam including Hoang Lien Son Range. Accordingly, this type of climate is also observed in the highland areas of Lang Cung mountain system in the southern part of Van Ban District. However, there exists few verifiable scientific data on this type of climate for

2 For herbarium collecting numbers in this expedition is used index “HAL”, which represent abbreviation of names of main participants of this project - Nguyen Tien Hiep, Leonid Averyanov and Phan Ke Loc (HAL 2001-2846).

the highland mountain areas in Viet Nam.

Basically, a humid climate with rainy warm summers and cold foggy and misty winters without a distinct dry period is typical for Van Ban highland area. The mean annual amount of precipitation according to meteorological data from the nearest comparable stations ranges from 2833 mm in Sa Pa town (22°20’N, 103°50’E, elev. 1570 m a.s.l.) to 3552 mm in Hoang Lien Son station (22°21’N, 103°46’E, elev. 2170 m a.s.l.) in the mountain regions of Hoang Lien Son Range to the NW of the studied area. The peak of rainfall comes here in the summer months. However no distinct dry period can be observed in this region. Morning dew is very common throughout mountain zone, as well as frequent heavy foggy mist. Humidity and amount of rainfall essentially increase with elevation in the mountains. Humid cold NE monsoon winds that bring heavy fog, mist and drizzling rain are very common here in the winter and early spring. They provide relatively high humidity on east and northeast facing mountain slopes, while much more dry habitat conditions may be regularly seen in the studied area on slopes of southwest exposure.

Temperature regime normally depends on elevation. The mean annual temperature at the nearest climate stations in Sa Pa weather station at 1570 m is 15.2°C, while it is 12.8°C in Hoang Lien Son at 2170 m a.s.l. Summer temperatures in these regions are usually around 16-20°C and winter temperatures regularly vary from 7-10°C. The absolute minimal temperature reported in mountains of Hoang Lien Son Range at elev. 2170 m a.s.l. is -5.7°C. Occasional wet snow and hail may be expected in the mountains of Van Ban District coldest winter months at elevations higher than 2000 m a.s.l. The maximum temperature recorded at this elevation is 24.9°C.

Considerable temperature variation connected with landscape elevation results in formation of clear altitudinal zones of vegetation in mountain regions of Hoang Lien Son Range. Generally, the climate zone of monsoon tropical climate associated with mountains defines formation in highland montane regions of northern Viet Nam of distinct zonal belt of montane forests at elevations higher than (1400) 1600 m , while at lower elevations submontane and lowland forests are primarily developed (Nguyen Khanh Van et al., 2000). This scheme is in accordance with basic world-accepted international classification of vegetation (UNESCO, 1973).

Closed evergreen tropical broad-leaved, mixed and coniferous wet submontane and montane forests are the dominant primary types of vegetation in highland zone of southern part of Van Ban District in the studied area.

Survey of primary vegetation in the studied area

Specific distribution of different climatic types, diverse soils, various geological structures and numerous geomorphologic forms, along with large range of landscape elevations lead to formation of four altitudinal zones with 4 main types of forests in the southern part of Van Ban District.

The primary zonal types of vegetation in the studied area belong to group of closed evergreen tropical monsoon (seasonal) forests, which have some modifications according to species composition of first forest stratum. The types of zonal primary

vegetation observed in southern part of Van Ban District are presented in Table 1. The distribution of dominant and associated tree species in canopy strata of these vegetation types is shown in Table 2. A number of azonal primary vegetation types that often have unusual plant communities with specific taxonomic composition rich in rare species are observed in each type of zonal vegetation. Such types of vegetation sometimes support very diverse and important habitats for many unique species of plants and animals. Among them are riparian vegetation that develops along stream and rivers, and lithophytic

Table 1

Types of primary zonal vegetation in southern part of Van Ban District

Name of formation Elevation in m a.s.l. Geomorphologic preference

1. Closed evergreen tropical monsoon (seasonal) forests: G-264G All available landscape forms

1.1. Lowland forests: G-6GG Not studied

1.1.a. Broad-leaved forests G-6GG Not studied

1.2. Submontane forests: 6GG-14GG All available landscape forms

1.2.a. Broad-leaved forests 6GG-14GG Lower and middle part of not too steep slopes

1.2.b. Mixed forests 6GG-14GG Upper part of more or less steep slopes

1.2.c. Coniferous forests 6GG-14GG Upper part of ridge slopes and tops of ridges

1.3. Lower montane forests 14GG-22GG All available landscape forms

1.3.a. Broad-leaved forests 14GG-22GG Lower and middle parts of not too steep slopes

1.3.b. Mixed forests 14GG-22GG Upper part of more or less steep slopes

1.3.c. Coniferous forests 14GG-22GG Upper part of ridge slopes and tops of ridges

1.4. Upper montane forests 22GG-264G All available landscape forms, but particularly on tops of ridges

1.4.a. Broad-leaved forests 22GG-264G Same

vegetation on open rocky outcrops and cliffs are very common in the studied area. Special attention was given to the study and description of such habitats during field work as localities of specific plant diversity of the area.

Brief survey of the types of primary zonal vegetation in the studied area

1.1. Closed evergreen tropical monsoon (seasonal) lowland forest [I.A.2a]3

This type of primary vegetation was represented on hills and mountain foothills at elevations 100-600 m a.s.l. Supposedly, broad-leaved warm loving forest formations were present in the past at these elevations in the studied area. This forest type is now completely extinct, being replaced in the area by secondary plant communities. Among them are the most common highly degraded open secondary forests, secondary stands of bamboo, secondary scrubs and grasslands. In the present study, these plant communities were not specifically studied.

3 Index according to UNESCO classification (1973).

Table 2

Distribution of main dominant and co-dominant species of the first and second forest strata at different elevations in mountains of Van Ban District and main forest types in this area

Distribution of species at different elevations in the studied area (Elevation is expressed on the table as numbers in hundred meters)

7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26

Acer laurinum

Acer sp.

Actinodaphne sp.

Archidendron balansae

Artocarpus sp.

Arundinaria sp.

Canarium sp.

Carpinus sp.

Castanopsis sp.

Cinnamomum sp.

Cryptocarya sp. 1

Dacrycarpus imbricatus

Dillenia sp.

Dipterocarpus retusus

Eberhardtia aurata

Elaeocarpus tonkinensis

Elaeocarpus sp.

Enkianthus sp.

Exbucklandia populnea

Ficus subincisa

Fokienia hodginsii

Gironniera subaequalis

Hopea mollissima

Illicium tsaii

Lauraceae gen.sp.

Forest type:

Note: Species observed as co-dominants of the first or second forest stratum at respective elevation is marked in Table 2 with black shading; species occurring at these strata as associates are marked with gray. Names of deciduous species are written in bold font. Vertical columns (delimited with bold lines) indicate different types of primary forests typical for the mountains of Van Ban District area: 1.2 - Closed evergreen tropical monsoon (seasonal) submontane broad-leaved, mixed and coniferous forests, 1.3 - Closed evergreen tropical monsoon (seasonal) lower montane broad-leaved, mixed and coniferous forests, 1.4 - Closed evergreen tropical monsoon (seasonal) upper montane broad-leaved forest.

1.2. Closed evergreen tropical monsoon (seasonal) submontane forests

[I.A.2b]

Remnant fragments of submontane forests may be found in the southern part of Van Ban District at elevations between 600 and 1400 m a.s.l. As main dominant trees of first forest stratum, warm-loving species appear to be common here. On level landscape formations, on not steep slopes, especially in the low and middle parts of mountain slopes are broad-leaved trees like Castanopsis sp., Cinnamomum sp., Dipte-rocarpus retusus, Hopea molissima, Madhuca pasquieri, Syzygium sp., Vatica sp., and warm loving species of Lithocarpus and Quercus. These trees reach 35-45 m high and form the first stratum of closed evergreen tropical monsoon (seasonal) submontane broad-leaved forests. Along tops of ridges, in upper part of mountain slopes, especially in dry conditions of more steep slopes, Dacrycarpus imbricatus appears as an important coniferous co-dominant in the first forest stratum. This tree together with the above mentioned broad-leaved trees form the closed evergreen tropical monsoon (seasonal) submontane mixedforests. Along relatively dry narrow and steep summits of ridges Dacrycarpus imbricatus occasionally may be observed as a single dominant of the first forest stratum forming closed evergreen tropical monsoon (seasonal) submontane coniferous forests. As the most common associates of the first and second forest strata that reach 25-30 m high in submontane forests appears numerous warm-loving broad-leaved trees, particularly: Artocarpus sp., Canarium sp., Cryptocarya sp., Dillenia sp., Eberhardtia aurata, Elaeocarpus tonkinensis, Elaeocarpus spp., Gironniera subaequalis, Litsea sp., Michelia spp., Nephelium milliferum, Xanthophyllum urophyllum and Livistona sp. (Table 2).

1.2.a. Closed evergreen tropical monsoon (seasonal) submontane broad-

leaved forests [I.A.2b(1)]

Altitudinal range in the studied area. 600-1400 m a.s.l.

Slope inclination and geomorphologic preference. Commonly 3-40(45)°. Flat valleys, basal parts, lower, or middle parts of mountain slopes.

Parent soil material. Granite, quartzite and quartzite sandstone.

Leaf litter. From 3 to 12 cm (commonly 4-8 cm) thick, overlaid by layer of fragments of unidentifiable leaves and twigs 1.5-3 cm thick.

Soil (depth of layer in cm from the surface). 0-20 - 25 cm - dark-brown,

gray-brown or brown, distinctly friable, rich in humus; 20-25 - 35-50 cm - yellow-brown, sandy-clayey, friable; 35-50 - 90-110 cm - yellow-orange, clayey, with numerous pieces of quartzite; 90-110 - 130-150 - bright orange, sandy-clayey, solid, with orange red soft sandy concretions and pieces of weathered parent rocks; 130150 cm and deeper - residuum of weathered granite, mixed with large pieces of quartzite placed on parent rocks.

1st forest stratum (tree storey). Common co-dominants (observed occasionally as oligo- or mono-dominants) are evergreen trees, such as Dipterocarpus retusus, Hopea mollissima, Madhuca pasquieri, Castanopsis sp. and Michelia spp. As occasional associates of first forest stratum are observed Canarium album, Para-michelia sp. and some representatives of Theaceae. Trees of this stratum reach (30-)40 - 45(-50) m high and (50-)70 - 100 cm in diameter. Projective coverage of this stratum varies in the studied area from (30-) 50 to 70%.

2nd forest stratum (tree storey). Most common co-dominants of this stratum in the studied area are evergreen trees like Hopea mollissima, Lithocarpus sp., and Michelia sp. As occasional associates are observed numerous evergreen trees, particularly species of Artocarpus, Cryptocarya, Litsea, Quercus, Vatica, Gleditsia, as well as Gironniera subaequalis, Nephelium milliferum, Xanthophyllum urophyllum, palm Livistona sp. Trees of this stratum commonly reach 20-35 m in high and 25 -50(-60) cm in diameter. Projective coverage in this storey varies from 30 to 60%.

3rd forest stratum (tree storey). As occasional co-dominants of this stratum may appear a giant bamboo - Dendrocalamus sp. and a few species of evergreen trees such as Adina sp. and Hopea mollissima. Commonly domination of any species in this stratum is not clear and forest stands is represented by numerous evergreen species, among which were observed Carallia brachiata, Elaeocarpus tonkinensis, Gironniera subaequalis, Knema globularia, Illicium majus, numerous species of such genera as Aglaia, Antidesma, Cinnamomum, Cryptocarya, Dillenia, Garcinia, Schefflera and many representatives of Annonaceae. Deciduous trees like Acer laurinum are also found here. Trees of this stratum usually reach 10-20 m tall and 1025 cm in diameter. Projective coverage of their canopies varies from 20 to 50%.

4th forest stratum (shrubs). Height of this stratum ranges usually from 3 to

7 m tall. Most common co-dominant species here are evergreen shrubs and treelets like Archidendron balansae, Aglaia edulis, Cinnamomum sp., Microdesmis caseari-folia, Oxyspora sp., Paralbizia sp. and Schefflera sp. Large bamboo - Dendrocalamus sp. and woody fern - Cyathea sp. are also observed as common co-dominants of shrub stratum in this type of forest. Numerous other evergreen shrub and treelet species were found here as more or less regular associates of this forest stratum. Among them are Aglaia edulis, Archidendron balansae, Carallia brachiata, Cinna-momum sp., Garcinia sp.,Macaranga sp.,Meliosma lepidota, Nephelium milliferum, Oxyspora sp., Pseudodissochaeta septentrionalis, Randia sp., Schefflera sp., Syzy-gium sp., numerous species of Ardisia, Lasianthus, Tabernaemontana and species of Annonaceae. Dwarf palm - Licuala paradoxa, middle tall bamboo and other giant herbs, such as Musa sp. are also common here, particularly in wet open places. Usual

projective coverage of this stratum varies from 20 to 30%.

5th forest stratum (undershrubs and herbs). Height of this stratum is less than 2 m. It includes numerous species of small shrubs, undershrubs and herbs. As more common co-dominants of this stratum were observed such shrubs as Strobilanthes sp., Blastus cochinchinensis, B. multiflorus, small palm Licuala sp. and woody fern Cyathea podophylla. Among herbs as co-dominant species were observed Mapania sp., Mondapsis petelotii, Ophiopogon latifolius, Ophiopogon sp., numerous species of Acanthaceae, as well as numerous terrestrial ferns like Asplenium normale, Polystichum spp. (3-4 species), Tectaria spp. (2 species) and selaginellas (Selaginella spp.).

A large number of species were observed in this stratum as occasional

associates. Among them were:

Shrubs:

Ardisia spp. (2-4 species), Dacrycarpus imbricatus (juvenile), Lasianthus spp. (3-4 species).

Calamus sp. (juvenile), Ilex sp. (juvenile), Myrsine sp.,

Dracaena sp., Ixora sp., Smilax sp.

Herbs:

Acanthaceae gen. sp., Costus speciosus, Pellionia sp.,

Aglaonema sp., Curculigo sp., Pentaphragma sinense,

Alpinia spp. (2 species), Elatostema spp. (2-3 species), Phrynium sp.,

Amorphophallus sp., Floscopa sp., Pilea sp.,

Anoectochilus roxburghii, Impatiens sp., Piper boehmeriaefolium,

Apostasia wallichii, Liparis paradoxa, Piper sp.,

Ardisia spp. (3 species), Mapania spp. (2 species), Scleria sp.,

Aspidistra sp., Mischobulbum cordifolium, Sonerila sp.,

Begonia spp. (5 species), Mondapsis petelotii, Tainia viridifusca,

Calanthe aleizettii, Ophiopogon latifolius, Tupistra albiflora,

C. densiflora, Ophiopogon sp., Vrydagzynea albida,

C. herbacea, Ophiorrhiza baviensis, Zeuxine nervosa,

C. lyroglossa, Ophiorrhiza spp. (2-3 species), Zingiber sp.

Fems and fem allies:

Bolbitis sp., Diplazium sp., Microlepia hookeriana,

Cyclosorus sp., Hemigramma decurrens, Pleocnemia leuzeana.

Diplazium donianum, Lindsaea javanensis,

The most common projective coverage of this forest stratum varies from (10-) 25 to 70%.

6th forest stratum (mosses and lichens). Few to many species of bryophytes less than 2 cm tall, mainly on decaying timber in shady places with projective coverage under than 2%.

Non-strata vegetation. Epiphytes and semi-epiphytes. Among the common species which form regular component of epiphytic plant communities in the forest of this type were observed typical epiphytic ferns Asplenium nidus, Aglao-morpha coronans, Davallia divaricata, Pyrrosia spp. (2 species), orchids - Eria thao, Callostylis rigida, Epigeneium amplum and creeping epiphytic lianas - Aeschy-nanthus spp. (2 species), Medinilla alternifolia, Pothos sp., Psychotria serpens

and Rhaphidophora decursiva.

A great number of associated species were found in epiphytic communities of broad-leaved submontane forests. Among them are numerous epiphytic mosses (representatives of Bryopsida that are particularly common at base of tree boles, on canopy branches and leaves, especially in shady places), ferns, orchids, and creeping epiphyte vines. Species most commonly observed here were:

Orchids (Orchidaceae):

Appendicula sp., Bulbophyllum affine,

B. insulsum,

Bulbophyllum spp. (3 species), Callostylis rigida,

Ceratostylis himalaica, Dendrobium acinaciforme,

D. chrysanthum,

Ferns:

D. nobile,

Dendrobium spp. (2-3 sp.), Epigeneium chapaense, Eria amica,

E. gagnepainei,

E. paniculata,

E. pannea,

E. siamensis,

Asplenium ensiforme,

A. wrightii,

Colysis digitata,

Elaphoglossum sp., Grammitis sp., Polypodium bourretii,

E. thao,

Flickingeria sp., Liparis chapaense, Pholidota chinensis, Schoenorchis gemmata, Sunipia scariosa, Trichotosia velutina.

Polypodium sp., Vittaria sp.

Epiphytic shrubs:

Rhododendron sp., Schefflera sp.

Creeping epiphytic vines:

Aeschynanthus sp., Ficuspumila,

Crepidomanes auriculatum, Lepisorus subrostratus,

Davallia divaricata, Medinilla alternifolia,

D. repens, M. pterocaula,

Dischidia sp., Piper sp.,

Pothos sp., Psychotria serpens, Rhaphidophora sp., Scindapsus sp., Vaccinium sp.

Woody vines and climbers are common. Among the regular lianas are Calamus sp., Korthalsia sp., Smilax sp., Stauntonia sp. and Tetrastigma spp. Occasionally observed associated herb and woody vine species in these forests are:

Acacia comosa,

A. pinnata,

Aristolochia sp.,

Bauhinia touranensis, Bauhinia spp. (2 species), Caesalpinia sp.,

Callerya cinerea, Dalbergia sp.,

Dischidia sp.,

Embelia pulchella, Entada pursathae, Fibraurea tinctoria, Fissistigma balansae, Gnetum sp.,

Paederia sp.,

Piper sp.,

Smilax spp. (2 species), Stauntonia sp.,

Strychnos sp.,

Tetrastigma planicaule, Tetrastigma sp.,

Vanilla annamica,

Vernonia sylvatica, Annonaceae gen. sp. (3 species). Asclepiadaceae gen. sp.

Numerous lithophytic species may be seen on rocky outcrops, especially on shady stream and river slopes in broad-leaved submontane forests. Most common lithophytes are numerous shade-loving mosses (including Polytrichum species, that

sometimes reach projective coverage on shady rocks up to 100%), ferns - Asplenium sp., Bolbitis sp., Leptochilus decurrens, Microsorum sp., Lepisorus spp. (3 species), Colysis digitata, C. pothifolia, Vittaria forrestiana, Vittaria sp. and herbs - Ophio-pogon latifolius, Pilea sp. and Tupistra albiflora.

Among plants of specific living forms in broad-leaved submontane forests were observed the canopy shrub semiparasite - Loranthus sp. and small mycotrophic achlorophyllous herbs, Didymoplexiopsis kiriwongensis (Orchidaceae) and Mono-tropastrum humile (Ericaceae).

1.2.b. Closed evergreen tropical monsoon (seasonal) submontane mixed forests [I.A.2b(1-2)]

Altitudinal range in the studied area. 960-1400 m a.s.l.

Slope inclination and geomorphologic preference. Commonly 20-40°. Upper parts of mountain slopes.

Parent soil material. Granite, quartzite and quartzite sandstone, commonly with numerous large quartzite dikes.

Leaf litter. From 4 to 8(-9) cm thick, overlaid by layer of fragments of unidentifiable leaves and twigs 1.5-3 cm thick.

Soil (depth of layer in cm from the surface). About 0-20 cm - dark-brown, gray-brown or brown, distinctly friable, rich in humus; 20-40 cm - yellow-brown, sandy-clayey, friable; 40 - 60-70 cm - yellow-orange, clayey, with numerous pieces of quartzite; deeper than 60 - 70 cm yellow, sandy-clayey mineral horizon of residuum and fragments of weathered parent rocks.

1st forest stratum (tree storey). Regular co-dominants (occasionally oligoor mono-dominants) are evergreen broad-leaved trees - Madhuca pasquieri, Litho-carpus spp. and conifers - Dacrycarpus imbricatus and Fokienia hodginsii. Elevatio-nal range of Dacrycarpus imbricatus in the belt of submontane forests in the studied area varies from 700 to 1400 m a.s.l. (Table 2), while Fokienia hodginsii was observed as co-dominant in this vegetation belt beginning from 900 m up to 1400 m a.s.l. or higher. Trees of this stratum commonly reach 40-45 m tall and 60-150 cm in diameter. Projective coverage of this stratum varies in the area from 50 to 60%.

Vertical and horizontal structure of other strata in submontane mixed forests, as well as character and species composition of their non strata component are very similar with the previous type of forest (1.2.a).

1.2.c. Closed evergreen tropical monsoon (seasonal) submontane coniferous forests [I.A.2b(2)]

Altitudinal range in the studied area. (900-)1300 - 1400 m a.s.l.

Slope inclination and geomorphologic preference. About 40°. Upper parts of mountain slopes and tops of ridge.

Parent soil material. Granite and sandstone, commonly with numerous large quartzite dikes.

Leaf litter. From 4 to 7 cm thick, overlaid by layer of fragments of unidentifiable leaves and twigs 2-3 cm thick.

Soil (depth of layer in cm from the surface). About 0 - 20(-25 cm) - dark-brown to brown, distinctly friable, rich in humus; 25-25 - 50-55 cm - yellow-brown to yellow, sandy friable; deeper than 50-55 cm - yellow-orange sandy-clayey mineral horizon of residuum and fragments of weathered parent rocks.

1st forest stratum (tree storey). Formed by mono-dominant stand of Fokienia hodginsii, which commonly reach 40 m high and 90-120 cm in diameter. Projective coverage of this stratum varies in the area from 50 to 60%. Dacrycarpus imbricatus may appear as occasional associate in the first forest stratum of these forests at 9001000 m a.s.l.

Lower strata in these forests are composed of broad-leaved trees. Vertical and horizontal structure of all lower strata in submontane coniferous forests, as well as character and species composition of their non-strata component are very similar to the broad-leaved forest type (1.2. a).

1.3. Closed evergreen tropical monsoon (seasonal) lower montane

forests [I.A.2c]

Relatively large areas of intact lower montane forests still exist in the southern part of Van Ban District between 1400 and 2200 m a.s.l. As main dominant trees of first forest stratum, species of moderate temperature conditions appear to be common here. On not too steep slopes, especially in low and middle part of mountain slopes main dominants are broad-leaved evergreen and deciduous trees, such as species of Acer, Archidendron, Cryptocarya, Eberhardtia, Exbucklandia, Lithocarpus, Quercus, Litsea, Magnolia, Manglietia, Michelia, Rehderodendron, Rhoiptelea, Schima, Symplocos etc. These trees reach 35-40 m high and form the first stratum of closed evergreen tropical monsoon (seasonal) lower montane broad-leaved forests. Along tops of ridges, in upper parts of mountain slopes, especially in dry conditions of more steep slopes in first forest stratum as an important co-dominant appears a conifer -Fokienia hodginsii. This tree together with broad-leaved trees forms the closed evergreen tropical monsoon (seasonal) lower montane mixed forests. Along relatively dry narrow summits of ridges having very steep slopes Fokienia hodginsii regularly is found as mono-dominant of the first forest stratum forming closed evergreen tropical monsoon (seasonal) lower montane coniferous forests. The most common tree-associates of the first and second forest strata reach 25-30 m high. In montane forests in the studied area, they are represented by a great number of broad-leaved evergreen and deciduous species (Table 2).

1.3.a. Closed evergreen tropical monsoon (seasonal) lower montane broadleaved forests [I.A.2c(1)]

Altitudinal range in the studied area. 1400-2200 m a.s.l.

Slope inclination and geomorphologic preference. About 40°. Middle and

lower parts of mountain slopes.

Parent soil material. Granite with numerous large quartzite dikes.

Leaf litter. From 5 to 7 cm thick, overlaid by layer of fragments of unidentifiable leaves and twigs 2-3 cm thick.

Soil (depth of layer in cm from the surface). 0 - 20 cm - brown, rich in humus; 20 - 40-50 yellow-brown to yellow, sandy-clayey; deeper than 50 cm was not observed.

1st forest stratum (tree storey). This stratum is commonly formed by broadleaved evergreen trees, such as Exbucklandia populnea, Rhodoleia championii and Lithocarpus sp. A deciduous tree Rehderodendron macrocarpum (which usually more typical for the second forest stratum) sometimes appears as occasional associate of this stratum. Trees here reach regularly 35-40 m tall and 70-100 cm in diameter. Projective coverage of this stratum varies in the area around 30%.

2nd forest stratum (tree storey). As most common trees in this stratum in the studied area are observed evergreen species like Cryptocarya sp., Lithocarpus sp., Schima wallichii and deciduous trees Rehderodendron macrocarpum and Rhoiptelea chiliantha. Trees of second forest stratum commonly reach 20-30 m high and 30-40 cm in diameter. Projective coverage of this storey is usually about 40%.

3rd forest stratum (tree storey). Usually certain domination of any species in this stratum cannot be seen, while forest stands here is represented by numerous evergreen species among which were observed Anneslea fragrans, Litsea sp., Symplocos sp. and Turpinia montana. Among deciduous representatives of this stratum most commonly occurs Acer laurinum. Trees of this stratum regularly reach 10-15 m tall and 10-20 cm in diameter. Observed projective coverage of their canopies varies from 20 to 25%.

4th forest stratum (shrubs). Arundinaria sp. and related bamboo species very often appear as co-dominants in forest understory. Among most common shrubby associates, here may be mentioned Ardisia sp., Illiciumpetelotii, Litsea sp.,Meliosma lepidota, Rhododendron cyanocarpum4 and Schefflera sp. All these species are evergreen shrubs 3-7 m tall. Total projective coverage in this stratum is usually 20-25%.

5th forest stratum (undershrubs and herbs). Height of the stratum is under 2 m. Sedges from such genera as Carex and Scleria are regular co-dominants in herb forest stratum. Other common associates on the forest floor are small shrub and undershrub species from such genera as Ardisia, Lasianthus, Pittosporum, Turpinia and Aucuba japonica. Numerous herbs and ferns also are very typical for the forest floor in montane broadleaved forests. Among them are such herbs as Alpinia sp., Asarum glabrum, Begonia sp., Hydrocotyle siamica, Lysimachia laxa, Ophiopogon sp., Paris polyphylla, Viola spp., and terrestrial ferns like Asplenium normale, Polystichum spp. (2 species), Tectaria sp. and Woodwardia unigemmata. Observed projective coverage of this stratum rare exceeds 5%.

4 Elevation - 1350-1400 m a.s.l. is observed as low limit of distribution of terrestrial shrubby Rhododendron species in studied area.

6th forest stratum (mosses and lichens). Few species that belong to Bryopsida (including Polytrichum sp.) 1-6 cm tall, commonly occur on wet decaying logs in shady places. Projective coverage do not exceeds 1-2%.

Non-strata vegetation. Epiphytes and semi-epiphytes. Epiphytic mosses occur abundantly, particularly on tree stems and canopy branches. Other dominants in epiphytic plant communities in these forests are ferns from such genera as Lepisorus and Pyrrosia. Among co-dominant species, which also commonly occur in broadleaved montane forests are other species of ferns and orchids. Among them are fern -Vittaria sp., orchids - Bulbophyllum hymenanthum, Bulbophyllum sp., Coelogyne lockii, Cymbidium floribundum, Epigeneium chapaense, Otochilus sp., Pholidota articulata and creeping epiphytic vines like Ficus pumila, Hedera chinensis and Piper sp. Climbers and lianas are not rare. Most commonly recorded species are large woody vines Acacia sp., Celastrus sp., Gnetum sp., Luvunga scandens, Staun-tonia sp., Tetrastigma planicaule, Tetrastigma sp. and climbing vine shrubs, like different species of Rubus. Lithophytes. Numerous mosses are common, particularly on rocks in shady wet places with occasional local coverage up to 100% and shade-loving ferns, such as Colysis elliptica and Phymatodes rhynchophylla.

Plants of specific life forms. Among specific living form was regularly observed a white mycotrophic achlorophyllous herb - Monotropastrum humile.

1.3.b. Closed evergreen tropical monsoon (seasonal) lower montane mixed forests [I.A.2c(1-2)]5

Altitudinal range in the studied area. 1640-2200 m a.s.l.

Slope inclination and geomorphologic preference. Varies from 15 to 40°. Upper parts of mountain slopes (usually of NE exposition) and summits of ridges.

Parent soil material. Granite, quartzite, hard highly metamorphosed sandstone with numerous large quartzite dikes.

Leaf litter. From 4 to 10 cm thick (up to 30 cm in local depressions), overlaid by layer of fragments of unidentifiable leaves and twigs 2-7 cm thick.

Soil (depth of layer in cm from the surface). 0 - 15-40 cm - brown to dark brown, rich in humus; 15-40 - 30-60 cm - gray to gray-brown; 30-60 - 70-110 cm -yellow to yellow-orange sandy-clayey horizon with pieces of weathered parent more or less large rocks and pieces of quartzite. In lower part of slopes are often observed numerous outcropping rocks and boulders.

1st forest stratum (tree storey). Regular coniferous co-dominant of this stratum is Fokienia hodginsii, which associates with such broad-leaved co-dominants as Cryptocarya sp., Lithocarpus spp. (2 species), Litsea sp., Magnolia sp., Michelia spp. (2 species), Rhodoleia championii and Schima wallichii. This group of trees includes some deciduous species, among which most commonly were observed Acer

5 Closed tropical monsoon (seasonal) evergreen montane broad-leaved forest with needle-leaved (coniferous) emergents is included in this vegetation category in this paper.

laurinum and Rehderodendron macrocarpum. As associated tree species occur Eberhardtia aurata and representatives of Sapindaceae. Common height of this stratum is 20-35 m. Trees reach 20-30(35) m tall and (30)40-70 cm in diameter. Usual projective coverage of this stratum is about 40-50%. In mountain slopes near the summits of ridges individuals of Fokienia hodginsii sometimes appear as emergents, which tower in matrix of continuous cover of broad-leaved trees. These emergent trees reach 40-50 m high with boles 110-150 cm in diameter. Projective coverage of their canopies is commonly not higher than 15-30%. Another rare coniferous emergent in these forests is Taiwania cryptomerioides, which was found in the studied area in highland valleys and on more or less reclined slopes at elevation 2000-2100 m a.s.l. (Nguyen Tien Hiep, Do Tien Doan, Phan Ke Loc, 2002). This rare indigenous tree reaches 30 m tall with boles more than 1 m in diameter. The discovery of T. crypto-merioides in the studied area outlines southern border of native distribution of this rare ancient tree, endemic to southern part of Eastern Asiatic floristic region.

2nd forest stratum (tree storey). Height of this stratum is (7)15-20(25) m with projective coverage 15-40%. Tree dominants here belong to evergreen species, among which most commonly found are Cinnamomum sp., Lithocarpus sp. and Symplocos sp. with bole diameter 15-40 cm. Regular associates are evergreen species like Actinodaphne sp., Eberhardtia aurata, Litsea sp., Meliosma lepidota, Quercus sp., Rhododendron sp., Rhoiptelea chiliantha, Schefflera sp. and Schima wallichii. An occasional deciduous tree in this stratum is Acer laurinum.

3rd forest stratum (tree storey). This stratum is not always clear pronounced. However, in some places its projective coverage may reach 40-50%. Trees here have commonly height 7-10 m tall with boles 10-15 cm in diameter. Most common species in this stratum are evergreen trees - Illicium petelotii, Myrsine sp., Rhododendron cyanocarpum and Rhododendron sp. In addition, juvenile samples of Fokienia hodginsii occur, as well as deciduous small trees Acer laurinum and Enkianthus sp. 4th forest stratum (shrubs). The stratum is usually clear pronounced and is formed exclusively by evergreen shrubby species. Height is 3-6(7) m with projective coverage up to 90%. Regular co-dominants are Illicium petelotii and middle tall bamboo species. Numerous associates include Actinodaphne pilosa, Actinodaphne sp., Aglaia sp., Aidia sp., Ardisia spp. (2 species), Carallia lucida, Ilex sp., Lasianthus spp. (3 species), Litsea sp., Meliosma lepidota, Myrsine sp., Oxyspora sp., Paralbizia sp., Phy-llanthus sp., Podocarpus neriifolius, Rhododendron cyanocarpum, Rhododendron spp. (2 species) and Schefflera sp., as well as a number of juvenile unidentifiable samples from Annonaceae, Euphorbiaceae, Lauraceae and Rubiaceae families.

5th forest stratum (undershrubs and herbs). The stratum includes shrubs, undershrubs, grasses, sedges and herbs up to 3 m tall. Projective coverage of this stratum varies from 2-3 to 60%. Among the most common shrubby species were observed Allomorphia sp., Lasianthus sp., Phyllagathis sp., as well as Arundinaria sp. and other related bamboo species. Co-dominant herbs and ferns in this stratum are Begonia sp., Diplazium maximum, Pilea spp. (2 species), Polystichum spp. (2 species), Pteris sp., Rumohra diffracta and Selaginella sp. Occasional shrub species occurring

here include such associates as Ardisia spp. (2 species), Croton sp., Fordiophyton strictum, Mycetia balansae, Oxyspora sp., Phyllanthus sp., Smilax sp., Tarenna sp., many representatives of Rubiaceae, juvenile samples of Calamus sp. and seedlings of Fokienia hodginsii. Occasional herbs, sedges, ferns and their allies are Alpinia sp., Anoectochilus roxburghii, Arisaema sp., Asplenium normale, Calanthe herba-cea, Carex spp. (2 species), Cephalantheropsis obcordata, Cymbidium ensifolium, Dianella nemorosa, Diplasium donianum, Disporum sp., Huperzia serrata, Ophio-pogon sp., Ophiorrhiza baviensis, Paris polyphylla, Peliosanthes teta, Pelio-santhes sp., Piper spp. (2 species), Plagiogyria sp., Polystichum sp., Scleria sp., Selaginella sp. and Stegnogramme scalani.

6th forest stratum (mosses and lichens). Cover of this stratum is found occasionally in more wet shady places and usually less than 1%. It is formed by few species of mosses from Bryopsida and Marchantiopsida 1-2 cm tall. They occasionally form continuous blanket with local coverage up to 100% on large roots, decaying logs and on large shady rocks.

Non-strata vegetation. Epiphytes and semi-epiphytes. Epiphytic communities in canopies of trees of first and second forest stratum are well pronounced and represented by numerous species of orchids, ferns and ericaceous plants. Among them most common are Bulbophyllum spp. (2 species), Ceratostylis himalaica, Coelogyne lockii, Coelogyne sp., Pholidota articulata, Pyrrosia sp., Rhododendron spp. (2 species) and Vaccinium spp. (2 species). Very common here are numerous species of Bryopsida with pendent shoots up to 15-20 cm long. Occasional associates in epiphytic communities of these forests were observed many other species of orchids (Bulbophyllum reptans, Bulbophyllum sp., Ceratostylis pygmaea, Epigeneium chapaense, Otochilus sp., Panisea tricallosa) and ferns (Asplenium ensiforme, A. prolongatum, Davallia divaricata, D. repens, Polypodium amplexicaule, Pyrrosia sp., Sclero-glossum minus, Vittaria sp.). Numerous epiphytic creeping vines are typical in forest of this type. Among them are very common Aeschynanthus spp. (2 species), Hoya sp., Hymenophyllum sp., Medinilla pterocaula, Piper sp., Pyrrosia sp., Scindapsus sp. and Vaccinium spp. (2 species). Climbers and lianas are common. They are represented by herbs and suffrutescent vines, like Crawfurdia sp., Embelia polypo-dioides, Jasminum sp., Piper sp., Rubus sp., Smilax spp. (2 species), Stauntonia sp., some species of Rubiaceae, as well as large woody lianas which may reach 20-35 m long (Celastrus sp., Dalbergia sp., Embelia pulchella, Korthalsia sp., Tetrastigma planicaule, Tetrastigma sp., representatives of Annonaceae and Menispermaceae). Lithophytic vegetation is observed in studied forests of this type on rocky slopes and in places of rocky outcrops. As common lithophytic undershrubs, here appear species of Ardisia and Strobilanthes, as well as woody fern Cyathea podophylla. Many species of different flowering plant families, as well as ferns and their allies are found here as herbaceous lithophytes. The most common among them are:

Aeschynanthus sp., Arisaema spp. (3 species), Diglyphosa evrardii,

Anoectochilus elvesii, Begonia spp. (2 species), Egenolfia sp.,

A. roxburghii, Colysis sp., Goodyerafoliosa,

G. viridiflora, Pilea spp. (3 species), Rhomboda petelotii,

Lepisorus spp. (2 species), Polypodium amplexicaule, Rumohra diffracta,

Leptochilus decurrens, Polystichum spp. (2 species), Selaginella sp.,

Ophiorrhiza baviensis, Primula sp., Trichomanes sp.

Ophiorrhiza sp., Pteris sp.,

A number of common lithophytic species in such habitats belong to Acanthaceae and Gesneriaceae. In more or less shady humid conditions, lithophytic mosses may reach coverage 100% in ground stratum.

Among plants of specific life forms were occasionally observed large achloro-phyllous orchid vine - Galeola nudiflora and dwarf white mycotrophic herb -Monotropastrum humile.

1.3.c. Closed evergreen tropical monsoon (seasonal) lower montane coniferous forests [I.A.2c(2)]

Altitudinal range in the studied area. 1460-2100 m a.s.l.

Slope inclination and geomorphologic preference. Varies from 0 to 60°. Upper parts of ridges slopes of any exposition, but particularly tops and summits of ridges.

Parent soil material. Granite, quartzite, hard highly metamorphosed sandstone with numerous large quartzite dikes.

Leaf litter. Commonly from 4 to 7 cm thick, overlaid by layer of fragments of unidentifiable leaves and twigs 2-3 cm thick.

Soil (depth of layer in cm from the surface). 0 - 15-30 cm - dark brown to brown, rich in humus; 15-30 - 35-70 cm - yellow-brown to yellow, sandy; (30-) 40-60 (-70) - 100-200 cm - yellow to yellow-orange (or occasionally yellow-brown) based on sandy-clayey mineral horizon of weathered parent rocks with more or less large pieces of sandstone and quartzite.

1st forest stratum (tree storey). Regularly first stratum of coniferous mountain forests in the study area is comprised of mono-dominant stands of Fokienia hodginsii. This giant cypress 40-50 m in height with bole diameter of 80-120 (-150) cm forms majestic pristine forests with projective coverage (40) 60-80%. Mature trees in these stands may be 1500-2000 years old. These forests represent one of the most endangered types of vegetation in the world. Occasional associates of the first stratum in coniferous forests are evergreen broad-leaved trees, such as Lithocarpus spp. (2 species) and Rhodoleia championii.

2nd forest stratum (tree storey). Evergreen co-dominants of this stratum are Cryptocarya sp., Eberhardtia aurata, Exbucklandia populnea, Lithocarpus sp., Manglietia sp., Michelia sp. Rhodoleia championii and Schima wallichii. Deciduous component of co-dominants include Rehderodendron macrocarpum and Rhoiptelea chiliantha. Trees of this stratum have height of (18-) 20-30 (-35) m and diameter of 30-50 (-70) cm.

3rd forest stratum (tree storey). Occasionally Rhododendron basilicum was observed as mono-dominant evergreen species in this stratum. However, commonly the stratum is represented by numerous associated evergreen and deciduous tree species that exhibit no certain dominance. Among them are evergreen trees, such as Archi-dendron balansae, Cryptocarya sp., Elaeocarpus tonkinensis, Litsea sp., Meliosma lepidota, Podocarpus neriifolius, Randia sp., Rhododendron cyanocarpum, Schefflera sp., and deciduous tree species Acer laurinum, Acer sp., Carpinus sp., Rhoiptelea chiliantha and Sorbus sp. Here also may be seen some species of Anacardiaceae and Sapindaceae. Common height of this stratum is 7-15 (-20) m with boles (10-) 15-25 cm in diameter. Projective coverage lies between 25 to 45%.

4th forest stratum (shrubs). Numerous evergreen species of shrubs and small trees 3-7 m tall form this stratum with usual projective coverage 20-60%. The most common co-dominant species here are Illicium petelotii, I. tsaii, Rhododendron cyanocarpum, Rhododendron spp. (5-8 species) along with such more or less common associates such as Actinodaphne pilosa, Actinodaphne sp., Ardisia sp., Canthium sp., Carallia lucida, Lasianthus spp. (2 species), Litsea sp., Macaranga sp., Meliosma lepidota, Myrsine sp., Oxyspora sp., Randia sp., Schefflera sp., saplings of Cinnamomum sp., Ilex sp., Podocarpus neriifolius, some species of Rubiaceae and woody fern Cyathea podophylla.

5th forest stratum (undershrubs and herbs). Height of this stratum commonly does not exceed 2-3 m. Its projective coverage may be only 5-10%, but usually varies between 30 and 60%. Among shrubs and undershrubs are commonly found such species as Ardisia spp. (2-3 species), Croton sp., Lasianthus sp.,Melicope pteleifolia, Oxyspora sp., Phyllagathis sp., Polygala sp., Rhododendron cinna-barium, Rh. ramsdenianum, Rh. wallichii, Smilax sp., some species of Rubiaceae, juvenile samples of Calamus sp. and Pandanus sp., as well as Arundinaria sp. and related genera of dwarf bamboo. Most common ferns, sedges and herbs here are Arachniodes sp., Asplenium normale, Begonia sp., Carex sp., Coryphopteris hirsuti-pes, Polystichum spp. (2-3 species), Scleria sp. and Sonerila spp. (2 species). Among their associates were observed Ainsliaea spp. (2 species), Alpinia sp., Anoectochilus roxburghii, Asplenium sp., Carex baccans, Curculigo sp., Ophiopogon sp., Osmunda banksiaefolia, Peliosanthes teta, Peliosanthes sp., Phyllanthus sp., Piper sp., Plagiogyria stenocarpa, P. yunnanensis, Polygala sp., Polystichum sp., Scleria sp., Selaginella sp. (2 species), Stegnogramme griffithii, Woodwardia unigemmata, some species of Gesneriaceae, Melastomataceae and numerous tree seedlings.

6th forest stratum (mosses and lichens). Commonly projective coverage of this stratum less than 1% and consist of species of Bryopsida and Marchantiopsida 0.5-3 cm tall growing only on large roots and decaying wood. However, in other places moss cover may reach 10-15% of ground. In such conditions occur many species of Bryopsida, among which most usual species of Polytrichum.

Non-strata vegetation. Epiphytes and semi-epiphytes. Epiphytes are abundant. Among the most common are ferns (Asplenium ensifolia, A. nidus, A. prolongatum, Davallia repens, Hymenophyllum sp., Lepisorus sp., Oleandra musi-

folia, Pyrrosia sp., Trichomanes sp.), orchids (Epigeneium chapaense, Coelogyne sp., Pholidota articulata) and ericaceous tuberiferous shrubby and vine species of Vaccinium and Rhododendron. Occasionally observed epiphytic species in this type of forest are:

Aeschynanthus spp. (2 species), Bulbophyllum emarginatum,

B. reptans,

Bulbophyllum spp. (2 species),

Callostylis rigida,

Coelogyne lockii,

Coelogyne sp., Cymbidium floribundum, Dendrobium longicornu, Dendrobium sp., Elaphoglossum sp., Hoya sp.,

Otochilus sp., Panisea tricallosa, Pholidota chinensis, Phymatodes sp., Polypodium sp., Vittaria sp.

Moss species play considerable role in epiphytic communities with projected coverage that often reaches 100% on tree stems and roots, particularly near the ground. Climbers and lianas. Small herb and suffrutescent vines, such as Smilax spp. (2 species) and Stauntonia sp. may be very common, but other vine species were observed only as occasional associates. Among these species were found Acacia sp., Alyxia sp., Calamus sp., Dalberghia sp., Embelia polypodioides, E. pulchella, Kadsura coccinea, Korthalsia sp., Miliusa sp. and some species of Rubiaceae. Some creeping epiphytic lianas (for example, Medinilla pterocaula, Piper sp., Vaccinium sp.) are also typical for these habitats, but large woody climbers here rather rare. Lithophytes. Among lithophytes commonly occur species of Begonia, Acanthaceae and numerous moss species, particularly from Bryopsida. Moss cover on rocks and boulders may often reach 100% of coverage, especially in shady places with more humid conditions.

Plants of specific life forms. In shady forest floor were often observed as a rather common species, mycotrophic achlorophyllous herbs - Monotropastrum humile, Petrosavia sinii, and ground root parasite Rhopalocnemis phalloides. Occasional semiparasitic liana up to 12 m long from Santalaceae family was observed in similar conditions.

1.4. Closed evergreen tropical monsoon (seasonal) upper montane forests

[I.A.2c]

1.4.a. Closed evergreen tropical monsoon (seasonal) upper montane broad-

leaved forests [I.A.2c(1)]

Altitudinal range in the studied area. 2200-2640 m a.s.l.

Slope inclination and geomorphologic preference. Varies in the studied area from 0 to 50°. Mountain tops of ridges of different direction, steep ridge slopes of any exposition in their upper part approximate to the mountain summits.

Parent soil material. Granite, quartzite, hard highly metamorphosed quartzite sandstone with numerous large quartzite dikes.

Leaf litter. Varies from (3-) 4-10 (-12) cm thick, overlaid by layer of fragments of unidentifiable leaves and twigs 1-3 cm thick.

Soil (depth of layer in cm from the surface). 0-(15)20-40(-60) cm - dark brown to brown, sometimes coming into black-brown to gray-brown in lower portion, rich in humus, often turfy, commonly very rich in rough quartzite sand. Soil with this horizon structure is often placed directly on mother parent rocks. In other cases on depth (30-)40-60 cm is observed horizon of gray to yellow-gray, sandy substrate, which is overlaid by yellow sandy-clayey mineral horizon with numerous fragments of weathered parent rocks and more or less large pieces of quartzite. Horizon of this structure commonly covers parent rocks on not too steep slopes or in small local depressions.

1st forest stratum (tree storey). First stratum of these forests includes in the studied area exclusively broad-leaved species6. On more or less gentle slopes, in leveled local depressions or small valleys between ridge peaks, forest stands of this type may reach 25-30 m tall with tree boles 40-70 cm in diameter. Main dominants of such forest stands are broad-leaved Lithocarpus spp. (2 species), Michelia sp., Rhodoleia championii, Schima wallichii and deciduous Acer laurinum. Projective coverage of this stratum is commonly about 50-70%.

2nd forest stratum (tree storey). As main co-dominants of this stratum commonly observed are evergreen species of Rhododendron, such as Rhododendron basilicum, R. cyanocarpum, R. ramsdenianum, Rhododendron spp. (2 species), Michelia sp. and deciduous Rehderodendron macrocarpum and Sorbus sp. that are 10-18 m tall with boles 20-30 cm in diameter. Projective coverage of this stratum is about 30%.

3rd forest stratum (shrubs). Height of this stratum is 4-7 m with common projective coverage of about 10%. Most common species here are Litsea sp., Rhododendron ramsdenianum, Rhododendron spp. (2 species), Symplocos sp. and deciduous Enkianthus sp.

4th forest stratum (undershrubs and herbs). Projective coverage of this stratum may reach 25-30(50)%. Height of plants here is under 3 m tall. Most common co-dominants are dwarf bamboo, such as Arundinaria sp., as well as Ardisia sp., some species of Euphorbiaceae and sedges (Scleria sp.). Associated undershrubs are Polygala sp., Rhododendron cinnabarium, and R. wallichii. Among herbs and ferns were occasionally observed Ainsliaea spp. (2 species), Goodyera schlechtenda-liana, Pedicularis sp. and Polystichum sp. Seedlings and saplings of Enkianthus sp., Schefflera sp. and some other woody species are also commonly present in this stratum.

5th forest stratum (mosses and lichens). Projective moss coverage 12 cm tall may reach on ground 4-6%. Among dominant species, there are few

6 Highest elevation limits in distribution of Fokienia hodginsii are observed in studied area at elevation about 2200 m a.s.l. At this elevation, Fokienia samples occur as occasional rather rare emergents in matrix of closed continuous canopy cover of lowest broad-leaved trees. This species was not observed in the area at highest elevation giving way to broad-leaved forests.

representatives of Bryopsida, particularly Polytrichum spp.

Non-strata vegetation. Epiphytes and semi-epiphytes. Among epiphytes dominate lichens, mosses and ferns. Lichens and mosses are very common, especially on tree boles near the ground and on canopy branches where they often form coverage up to 100%. Most common fern species in epiphytic communities here are Hymeno-phyllum sp., Oleandra musifolia, Trichomanes sp., with associated species, such as Elaphoglossum sp., Lepisorus sp., Phymatodes sp., Polypodium sp., Pyrrosia sp. and Vittaria sp. Ericaceous epiphytic shrubs and epiphytic creeping vines (Rhododendron sp. and Vaccinium spp.) are also very common, while orchids become rare. Among orchids here occasionally were observed very few species, such as Bulbo-phyllum reptans, Coelogyne sp. and Dendrobium sp.7 A not so rare flowering plant epiphyte, Polygonatum punctatum, was found in this forest. Climbers and lianas. Climbers are rather rare, among occasionally observed species are small suffrutescent vines like Embelia polypodioides and Smilax sp.

Plants of specific life forms. Dwarf mycotrophic achlorophyllous herbs -Monotropastrum humile and Petrosavia sinii, as well as canopy parasitic shrubs Loranthus sp. and Viscum articulatum are occasionally common.

On very step slopes, along narrow ridges and on mountain tops tall forest stands give way to undersized dwarf cloud mountain forest8.

First forest stratum is represented here by gnarled trees 4-6 m tall with boles 20-35 cm in diameter. Aside from already mentioned species (Lithocarpus spp., Michelia sp., Rhodoleia championii, Schima wallichii, Acer laurinum) in first stratum of such forests appear numerous species of Ericaceae - Rhododendron basilicum, R. cyanocarpum, R. ramsdenianum, Rhododendron spp. (2 species), Pieris sp., as well as Illicium tsaii and Symplocos sp. Among deciduous trees, here are very common species of temperate genera, such as Enkianthus, Sorbus and Acer. Projective coverage of this stratum ranges from 50 to 80%.

Forest understory is represented by small trees and gnarled treelets about 3-4(-5) m tall. They form total projective coverage 40-60(-70)% and include numerous evergreen and deciduous rhododendrons - Rhododendron cinnabarium, Rh. ramsdenianum, Rh. wallichii, Rhododendron spp. (2-3 species), Daphne sp., Ilex sp., Linocera sp., Myrsine sp., Schefflera sp., Vaccinium dunalianum, some species of Lauraceae, deciduous Pieris sp., Vaccinium sp. and dwarf bamboo (Arundinaria sp.), which often form very dense thickets.

Herb stratum is usually less than 1 m tall with usual projective coverage of only 5-10%. It includes such ferns, herbs and undershrubs as Ainsliaea spp. (2 species),

7 Basically most epiphytic orchids in studied area have elevation limits at 2200-2250 m a.s.l. and were not observed at higher elevation, where lichens, mosses, ferns and species of Ericaceae appear as a regular co-dominants in epiphytic communities.

8 These low, wind formed broad-leaved montane forests that are observed on high mountain tops in studied area may be interpreted as azonal derivatives of closed evergreen tropical monsoon (seasonal) montane broad-leaved forests - I.A.2c(1).

Dryopteris sp., Goodyera schlechtendaliana, Ophiopogon spp. (2 species), Pedicu-laris sp., Plagiogyria yunnanensis, Polygala sp., Polystichum sp. and Smilax sp.

Ground stratum in forests of this type includes lichens (many species, mainly Cladonia), mosses (many species, including Polytrichum spp. and Sphagnum spp.) and dwarf moss-like ferns - Hymenophyllum sp. and Trichomanes spp. (2 species). This stratum has height of under 3(-5) cm and projective coverage from 1 to 50%.

Epiphytic mosses and lichens are likewise abundant. They commonly cover tree stems and branches with continuous massive cover drooping partially up to 10-15 cm from along horizontal branches. Other common epiphytes in this forest are ferns, particularly such species as Elaphoglossum sp., Grammitis sp., Hymenophyllum sp., Lepisorus sp., Phymatodes sp., Pyrrosia sp. and Trichomanes spp. (2 species). Angio-sperm epiphytes are rare. Among them here were observed Polygonatum punctatum and few ericaceous species (mainly Rhododendron and Vaccinium). Climbers and lianas include small herbaceous and frutescent vines like Ampelopsis sp., Crawfurdia sp., Rubus sp. and Smilax sp. Creeping lithophytic vine species of Vaccinium commonly cover open rock outcrops and cliffs. On tree tops were occasionally observed parasitic shrubs, which belong to Loranthaceae (Loranthus sp.), Santalaceae and Viscaceae (Viscum articulatum).

Azonal types of vegetation

The most common and important types of azonal vegetation in the studied area are plant communities on open rocky cliffs and riparian plant communities that may be seen along rocky streams and along lower part of stream canyons. All these vegetation types represent specific derivatives of zonal primary montane and submontane forests. At the same time, these habitats accumulate and support very high level of plant species diversity, especially rich in rare lithophytic species that rarely occur under shady canopies of primary forest.

Lithophytic plant communities on open granite cliffs

Lithophytic plant communities may be observed along all altitudinal range of the studied area. However, they represent a critically endangered type of vegetation easily destroyed by forest fire or desertification connected with logging of the forest. Under the pressure of these factors, lithophytic communities rapidly lose major parts of primary elements, regeneration of which is very questionable.

The described primary lithophytic communities on exposed rocky granite and quartzite outcrops and cliffs lie in zone of closed evergreen tropical monsoon (seasonal) lower and upper montane broad-leaved, mixed and coniferous forests and represent their derivative. These communities are probably most typical for pristine nature of the studied region at elevation (1700-)1800-2300 m a.s.l.

Cliff inclination in studied habitats ranged from 70 to 80° that provide probably most optimal condition for formation of typical lithophytic cliff plant communities. Leaf litter

and very thin soil accumulated here only in cliff crevices, narrow shelves, and occasional small pockets in bluffy rocks composed in the studied area commonly with granite having numerous large quartzite dikes. Soils here, when present, are hardly developed, gray-black or gray-brown, sandy, based on rough quartzite sand deposits accumulated in pockets and occasional depressions of parent rocks. Under moss pillowy cover are commonly observed 1-3 cm turf deposits.

In the first stratum on granite cliffs occasionally may be seen some trees and shrubs 3-10 m tall that form sometimes projective coverage up to 30-40%. Among most common woody species observed here are evergreen Ficus subincisa, Rhododendron cyanocarpum, Rhododendron sp., Schefflera spp. (2 species) and Tetrapanax papyrifera. Deciduous trees and shrubs, such as Acer laurinum, Rehdero-dendron macrocarpum, Rhoiptelea chiliantha and Sorbus sp. represent considerable portion in these stratum. In more steep part of slopes this stratum may be absent.

Herb and undershrub stratum is represented by genuine lithophytic species usually 10-150 cm tall. Commonly projective coverage of this stratum 20-40%, but on very steep cliffs and vertical rocks cover may be less than 10%. Among regular dominants here were observed Carex sp., Selaginella sp., Panicum bisulcatum and other grasses including dwarf bamboo (Arundinaria sp.). Most usual shrubby associates are Hypericum hookerianum, Polygala sp., Rhododendron cinnabarium, R. rams-denianum, Rhododendron spp. (2 species), Sporoxeia sp., Vaccinium dunalianum, Vaccinium spp. (2 species). Herbs and ferns are various, including the following species:

Ainsliaea spp. (2 species), Alpinia sp.,

Asplenium normale, Coelogyne lockii, Coelogyne sp.,

Curculigo sp., Cymbidium floribundum, Dendrobium sp.,

Elaphoglossum sp.,

Gentiana sp.,

Goodyera schlechtendaliana, Lepisorus macrocarpus, Lepisorus spp. (2 species), Oreocharis aurea,

Pholidota articulata, Phymatodes rhynchophyllus,

Phymatosorus sp.,

Pleione grandiflora, Polypodium spp. (2 species), Polystichum spp. (2 species), Scleria sp.,

Sonerila sp.,

Vittaria forrestiana.

In open places particularly on south-facing cliffs, creeping xerophytic ferns and lycopodiums become common. Among them are Dicranopteris linearis, D. splen-dida, Dicranopteris sp., Lycopodium casuarinoides, L. clavatum, L. complanatum and Pyrrosia sp.

Ground stratum includes numerous species of lichens (particularly numerous species of Cladonia), mosses (particularly species of Polytrichum and Sphagnum), as well as some dwarf lithophytic ferns and their allies like Cheilanthes sp., Huperzia serrata and Scleroglossum sp. On sunny dry vertical cliffs may be commonly seen dense pillows of Sedum vietnamense settled in small rocky crevices. Height of this stratum is 1-5 cm tall. It may reach coverage on ground 40-60% of total surface.

Epiphytes in cliff shrubby communities are very common and often abundant. They include numerous species of lichens, mosses, ferns, and orchids. Commonly observed epiphytic species include Bulbophyllum emarginatum, B. reptans, Bulbo-

phyllum spp. (2 species), Coelogyne lockii, Coelogyne sp., Cymbidium floribundum, Dendrobium longicornu, Dendrobium sp., Epigeneium chapaense, Eria coronaria, E. siamensis, Otochilus sp., Pholidota articulata, Vittaria sp., as well as creeping epiphytic vines Hoya sp., Polypodium sp. and Pyrrosia spp. (2 species). Epiphytic lichens and mosses often completely cover branches of small gnarled trees and shrubs with pendant limbs up to 15-20 cm.

Climbers, lianas and climbing shrubs are numerous and diverse. Among the most common found species are Albizia sp., Celastrus sp., Gnetum sp., Hedera chinensis, Jasminum sp., Luvunga scandens, Rubus alcaeafolius, Rubus sp., Smilax sp., Stauntonia sp., Tetrastigma sp. and some species of Rubiaceae. Some of these species form on vertical cliffs dense spiny impassable thickets.

Among plants of specific life forms are remarkable annual ephemeral species, which settle in Sphagnum pillows and develop a new generation during rainy season when substrates are constantly filled with water. Among such plants were observed species of Eleocharis sp. and Utricularia sp. Some perennial ephemeroid herbs occurring here also belong to this ecological group. Among them are undescribed species of Begonia with spherical underground tubers and pseudobulbous orchids, such as Pleione grandiflora, large colonies of which were found in the studied area (Averyanov et al., 2002; Averyanov, Phan Ke Loc, 2002). Canopy parasitic shrubs like Loranthus sp. and Viscum articulatum are rather regular component of shrubby lithophytic communities all over thee studied area.

Riparian plant communities along rocky mountain stream and lower part of stream canyons

The most rich and typical primary riparian plant communities in the studied area were found and described in mountain belt at elevation 600-1000 m a.s.l., where they represent derivative of closed evergreen tropical monsoon submontane broadleaved and mixed forests - I.A.2b(1); I.A.2b(1-2). Riparian communities spread along small mountain rivers in humid, more or less shady deep rocky stream valleys, canyons and waterfalls. These habitats support very high level of plant diversity including numerous tree, shrub and herb humid-loving species. Commonly these azonal communities accumulate all plant diversity of surrounding parent forest.

The inclination of river valleys in the studied area averages between 5-10°. The bottom of streambed is composed with rocks and large boulders. Bluffy outcrops of parent rocks commonly appear on lower part of steep river slopes, on sides of narrow stream canyons and on waterfall cliffs. Granite with large quartzite dikes and occasionally pure white quartzite are usual parent rocks in the studied area observed along mountain streams. Alluvial deposits of rough quartzite sands are very common along bottom of river valleys, particularly in more flat places, where they may reach 1 m in depth. Leaf litter on river slopes reaches usually 4-6 cm in thick. It is overlaid by 1-3 cm layer of unidentified decomposed fragments of leaves and twigs. Soils in lower part of river slopes include dark gray- or black-brown, sandy, very friable, upper horizon

20-30 cm in thick rich in humus. On depth of30-50 cm gray sand is commonly observed. Deep down may be seen yellow sand with soft concretions of weathered rocks overlaid by residuum derived from parent rocks.

In first forest stratum in riparian plant communities in the studied area may be commonly seen evergreen trees, such as Castanopsis sp., Dacrycarpus imbricatus, Hopea mollissima, Lithocarpus sp. and Michelia sp. They are main dominants of this stratum, which reach 35-45 m tall and 60-100 cm in diameter with projective coverage 50-60%.

Trees of second forest stratum usually reach 18-25(-30) m high with diameter of boles ranging between 20-35 cm. Projective coverage of their canopies about 4550%. Evergreen species dominate here. Among them most common are Cinnamomum sp., Dillenia sp., Dysoxylum sp., Elaeocarpus tonkinensis, Elaeocarpus sp., Giron-niera subaequalis, Lithocarpus sp., Macaranga sp., Platea latifolia, Chisocheton sp., Syzygium sp. and some representatives of Sapindaceae. Choerospondias axillaris is alone deciduous tree typical for this stratum.

Third forest stratum commonly is well pronounced. It reaches 10-15 m in height with projected coverage 30-40%. Very common here are stands of Dendro-calamus sp., Schizostachyum dullooa and other related species of woody bamboo. Trees of this stratum have commonly boles 10-18 cm in diameter. All tree species are evergreen. Most commonly observed species are Aglaia sp., Anneslea fragrans, Cryptocarya sp., Dillenia sp., Eberhardtia aurata, Litsea sp., Miliusa sp., Schefflera sp. and Turpinia sp.

Numerous evergreen shrubs form shrub understory in riparian plant communities. The domination of any certain species usually is not observed, but general diversity of shrub species commonly is very high. Among regular species occurring here that may be mentioned are Aralia chinensis, Archidendron balansae, Ardisia sp., Blastus cochinchinensis, Brassaiopsis glomerulata, Carallia brachiata, Euonymus sp., Ficus spp. (3 species), Gomphandra sp., Lasianthus spp. (3 species), Melastoma sp., Meliosma lepidota, Pseudodissochaeta septentrionalis, Sterculia sp., Trevesia palmata, Turpinia sp., Villebrunea integrifolia, some species of Euphorbiaceae and saplings of Dacrycarpus imbricatus. Woody ferns (Cyathea contaminans, C. salettii, Cyathea sp.), dwarf palms and palm-like plants (Licuala paradoxa, Pandanus sp.) and giant herbs, such as Amomum sp. and Musa sp. are very typical for these habitats. All mentioned plants form understory stratum 3-7 m tall with usual projective coverage 20-30%.

Undershrubs, ferns and herbs under 2(2.5) m tall form along rivers lush vegetation with projective coverage up to 40-50%. Blastus cochinchinensis, Strobilan-thes spp. (2 species), as well as other representatives of Acanthaceae are usual undershrub dominants on wet river slopes. Here also are commonly found some grasses (Cyrtococcum sp.), sedges (Cyperus spp., Fimbristylis sp., Kyllinga spp.), ferns and their allies (Cyclosorus sp., Selaginella sp., Tectaria spp., Thelypteris sp.) and creeping moist-lowing herbs, such as Hydrocotyle spp. (2 species), Pellionia spp. (2 species), Pilea sp., Pratia nummularia and Viola spp. (3 species). Among regular shrub asso-

ciates of this stratum were observed Aralia armata, Ardisia spp. (3 species), Breynia sp., Dracaena sp., Ficus sp., Lasianthus spp. (2 species), Mycetia balansae, Pandanus sp., Psychotria sp. and Schefflera sp. Herbaceous species composition is very diverse and includes many species of herbs, grasses, sedges, ferns and fern allies. Among commonly observed associates in this group are:

Abacopteris sp., Acanthephippium striatum, Aglaonema sp.,

Alpinia sp.,

Amomum sp., Amorphophallus sp., Angiopteris sp.,

Arisaema sp.,

Aspidistra sp.,

Begonia spp. (2 species), Blechnum orientale, Calanthe herbacea,

C. lyroglossa,

Collabium assamicum, Colocasia sp.,

Colysis digitata,

Costus speciosus, Curculigo sp.,

Cyrtococcum sp., Dianella nemorosa, Diplazium donianum,

D. maximum,

Disporum sp., Gonatanthus pumilus, Hapaline aff. colaniae, Hedychium sp., Histiopteris incisa, Homalomena occulta, Impatiens sp.,

Liparis paradoxa, Mapania spp. (2 species), Mischobulbum cordifolium Mondapsis petelotii, Ophiopogon latifolius, Ophiopogon sp., Ophiorrhiza baviensis,

Ophiorrhiza sp., Pentaphragma sinense, Phaius mishmensis, Phrynium sp.,

Piper boehmeriaefolium, Piper sp.,

Plectranthus sp.,

Pollia sp.,

Polygonatum sp.,

Scleria sp.,

Selaginella sp.,

Sonerila sp., Sphenomeris chinensis,

, Tacca plantaginea, Vrydagzinea albida, Zingiber sp.

Mosses and lichens occasionally forming ground stratum are not common. Few species of mosses (particularly Bryopsida and Marchantiopsida) sometimes form cover 2-3% in wet shady places, but often this stratum is absent.

Numerous epiphytes are very typical in riparian forests in the studied area. They form integral characteristic element of this habitats including large numerous clumps of epiphytic nest ferns, such as Asplenium nidus and Aglaomorpha coronans. Another epiphytic dominants are other ferns and orchids, particularly Appendicula cornuta, Coelogyne fimbriata, Epigeneium chapaense, Lepisorus spp. (4 species), Nephrolepis cordifolia, Rhynchotechum sp. and Selliguea lateritia. Creeping epiphytic lianas and climbers occur abundantly, covering sometimes boles of all large trees in shady slopes along rivers. Among the very common species are Aeschynanthus spp. (3 species), Davallia divaricata, D. repens, Dischidia sp., Ficus pumila, Hoya sp., Medinilla alternifolia, M. pterocaula, Pothos sp., Psychotria serpens, Pyrrosia sp., Rhaphidophora sp. and Scindapsus sp. Many species of mosses (particularly from Bryopsida) completely cover branches of trees above streams, hanging often up to 15-20 cm.

The more or less common associated epiphytic species here are as follows:

Asplenium prolongatum, Bulbophyllum insulsum,

E. pusilla,

E. siamensis,

Oberonia sp., Pholidota chinensis,

B. penicillium,

Bulbophyllum spp. (2 species),

Coelogyne fimbriata,

Eria amica,

Grammithis sp., Hymenophyllum sp., Lepisorus sp., Liparis chapaense, L. petelotii,

L. stricklandiana,

Trichomanes sp., Trichotosia velutina, Vaccinium sp., Vittaria elongata.

E. gagnepainei,

E. paniculata,

Lianas and climbers in riparian plant communities reach highest diversity in the area. Among main dominant species are giant woody vines 30-40 m long with characteristically flat undulated stems up to 40 cm wide, such as Tetrastigma planicaule, Tetrastigma sp. and Bauhinia spp. (2 species). Here also are numerous other woody and herb lianas like Acacia pinnata, Albizia sp., Bauhinia touranensis, Clematis sp., Dalbergia sp., Desmos chinensis, Embelia pulchella, Fissistigma balansae, Gnetum sp., Paederia sp., Piper sp., Rubus spp. (3 species), Smilax spp. (2 species), Stauntonia sp., Strychnos sp., Uncaria sp., Vernonia sylvatica, Vernonia sp., Zantho-xylum sp., as well as numerous immature representatives of Annonaceae, Apocynaceae and Rubiaceae.

Wet stream boulders, rocky outcrops on river slopes and waterfall cliffs are habitats of many lithophytic species, particularly ferns, such as Abacopteris sp., Angiopteris somae, Angiopteris sp., Asplenium prolongatum, Blechnum orientale, Bolbitis sp., Colysis digitata, Elaphoglossum sp., Leptochilus sp., Nephrolepis cordifolia., Osmunda vachellii, Vittaria forrestiana. Other common lithophytes in riparian communities are Acorus gramineus, Amorphophallus sp., Begonia spp. (5 species), Bulbophyllum sp., Carex sp., Costus speciosus, Dendrobium chrysanthum, Ficus pyriformis, Heterogonium sp., Liparis stricklandiana, Ophiopogon latifolius, Pellionia spp. (4 species), Pholidota chinensis, Pilea sp., Steudnera sp. and Tupistra albiflora. Moss species (particularly from Bryopsida and Marchantiopsida) often cover 100% of surface of shady wet stream rocks. Among lithophytic creeping vines very common Ficus pumila and Pyrrosia sp.

Plants of specific life forms include characteristic epiphytic shrub - Schefflera sp., epiphytic climbing tree - Fagraea ceylanica, and epiphytic tree-stranglers - Ficus spp. (2-3 species).

General notes on the flora

Like any montane floras, the highland flora of mountains of Van Ban District has a complex character. At low elevations up to 1400 m a.s.l., in mountain belt of lowland and submontane forests it is comprised mainly of warm loving elements. This is genuine tropical flora, which approaches the typical floras of North Indochinese Province of Paleotropic floristic kingdom (Averyanov, et al., 2003). However, at higher elevations, in the belt of lower montane and upper montane tropical woods, the flora acquires temperate character, which approximates the floras typical for Sikang-Yunnan floristic province of Holarctic floristic kingdom. Thus one of the key important floristic

borders of Asia, lies in Van Ban montane uplands at elevations about 1400 m a.s.l. This line separates Holarctic and Paleotropic floristic realms. According to taxonomic composition, both components of the flora may be classified as rather tropical floras.

Like any other tropical floras, the flora of Van Ban mountains includes considerable portion of orchids and ferns. Both these groups fill the first position in the top ten families in the flora, that underlines its tropical character (Tolmachev, 1974). According to preliminary estimation each of these groups include from 6 to 8% of plant species occurring in the studied area.

Most orchids in Van Ban area are usually epiphytic. Among the most common species are:

Agrostophyllum brevipes, Dendrobium acinaciforme, L. mannii,

Appendicula hexandra, D. aduncum, L. petelotii,

Biermannia calcarata, D. brymerianum, L. stricklandiana,

Bulbophyllum affine, D. chrysanthum, Monomeria barbata,

B. atrosanguineum, D. longicornu, Oberonia pumilio,

B. bisetoides, D. nobile, Otochilus sp.

B. emarginatum, D. thyrsiflorum, Panisea tricallosa,

B. hymenanthum, Epigeneium chapaense, Pholidota articulata,

B. insulsum, Eria amica, Ph. chinensis,

B. penicillium, E. gagnepainii, Schoenorchis gemmata,

B. reptans, E. paniculata, Sunipia scariosa,

B. retusiusculum, E. pannea, Thrixspermum formosanum,

Callostylis rigida, E. pusilla, Trichotosia dasyphylla,

Ceratostylis himalaica, E. siamensis, T. microphylla,

C. pygmaea, E. thao, T. velutina,

Coelogyne fimbriata, Gastrochilus calceolaris, Vanilla annamica.

C. lockii, Liparis chapaensis,

Cymbidium floribundum, L. distans,

Terrestrial orchids also form a rather large ecological group, among which

the following regularly observed species:

Acanthephippium striatum, C. lancifolium, Rhomboda petelotii,

Anoectochilus elwesii, Erythrodes blumei, Spiranthes sinensis,

A. roxburghii, Goodyera foliosa, Tainia angustifolia,

Apostasia wallichii, G. fumata, T. latifolia,

Calanthe aleizettii, G. schlechtendaliana, T. viridifusca,

C. densiflora, G. viridiflora, Tropidia angulosa,

C. herbacea, Hetaeria biloba, Vrydagzynea albida,

C. lyroglossa, Liparis paradoxa, Zeuxine nervosa,

Cephalantheropsis obcordata, Mischobulbum cordifolium, Z. parvifolia.

Collabium assamicum, Phaius mishmensis,

Cymbidium ensifolium, Platanthera angustata,

Other orchids in Van Ban area are obligate lithophytes (Diglyphosa evrardii, Diplomeris pulchella, Pleione grandiflora) and achlorophyllous mycotrophic saprophytes (Didymoplexiopsis khiriwongensis, Galeola nudifolia, Lecanorchis javani-ca). The total number of orchid species in the flora of Van Ban mountain area may be initially estimated at 160-180 species.

Ferns are the next largest taxonomic group in the mountain flora of Van Ban District. The most common species observed here are:

Angiopteris somae, Anogramme microphylla, Arthromeris wallichiana, Asplenium cheilosorum,

A. ensiforme,

A. griffithianum,

A. laciniatum,

A. lepturus,

A. nidus,

A. normale,

A. prolongatum,

A. pseudolaserpitifolium, A. tenerum,

A. tenuifolium,

A. wrightii,

Blechnum orientale, Bolbitis appendiculata,

B. christensenii, Cheiropleuria bicuspis, Colysis digitata,

C. dissimilialata,

C. longisora,

Coniogramme intermedia, Coryphopteris hirsutipes,

Crepidomanes auriculatum, Crypsinus griffithianus,

C. rhynchophyllus,

Cyathea contaminans,

C. gigantea,

C. podophylla,

C. spinulosa,

Cyrtomium fraxinellum, Davallia divaricata,

D. repens,

Diacalpe aspidioides, Diplazium dilatatum,

D. donianum,

D. griffithii,

D. pullingeri,

D. sorzogonense,

Dipteris chinensis, Elaphoglossum angulatum, Lepisorus obscuro-venulosa, L. subrostratus,

L. thunbergianus, Leptochilus decurrens, Lindsaea javanensis, Loxogramme salicifolia,

Microlepia hookeriana, Monachosorum henryi, Neocheiropteris ningpoensis, Onychium lucidum,

Osmunda banksiaefolia,

O. vachellii,

Phymatosorus lucidus, Plagiogyria stenoptera,

P. yunnanensis,

Pleocnemia irregularis, Polypodium amoenum,

P. bourretii,

Polystichum squarrosum,

P. tsus-simense,

Pyrrosia porosa, Scleroglossum minus, Selliguea lateritia, Stegnogramme griffithii, Tectaria simonsii,

T. subtriphylla,

T. yunnanensis,

Vittaria forrestiana, Woodwardtia unigemmata.

They belong to such tropical families as Adiantaceae, Aspleniaceae, Blechna-ceae, Cyatheaceae, Davalliaceae, Dennstaedtiaceae, Dipteridaceae, Dryopteridaceae, Grammitidaceae, Hymenophyllaceae, Lomariopsidaceae, Marattiaceae, Osmundaceae, Plagiogyriaceae, Polypodiaceae, Thelypteridaceae, Vittariaceae and Woodsiaceae. Among living forms, here dominate epiphytes, terrestrials and lithophytes. Significant role in habitats have woody ferns, which are very common in the studied area at elevations 700-1100 m a.s.l.

Among other largest families, representatives of which play first role in taxonomic composition of the whole flora may be mentioned Annonaceae, Cyperaceae, Ericaceae, Euphorbiaceae, Gesneriaceae, Lauraceae, Melastomataceae, Myrsinaceae, Rubiaceae and Urticaceae. At the same time in lowland and submontane wood formations at low elevation first role in first and second forest strata belongs to such

genuine tropical families as:

Anacardiaceae (Choerospondias axillaris),

Dipterocarpaceae (Dipterocarpus retusus, Hopea mollissima),

Elaeocarpaceae (Elaeocarpus petiolatus, E. tonkinensis, Elaeocarpus sp.), Fabaceae (Albizia sp., Archidendron balansae, Ormosia sp.),

Lauraceae (Cinnamomum sp.),

Meliaceae (Aglaia edulis, Aglaia sp.),

Moraceae (Ficus spp.),

Myristicaceae (Knema globularia),

Myrtaceae (Syzygium spp.),

Podocarpaceae (Dacrycarpus imbricatus),

Polygalaceae (Xanthophyllum urophyllum),

Proteaceae (Helicia spp.),

Rhizophoraceae (Carallia brachiata, C. lanceaefolia),

Sapindaceae (Nephelium milliferum),

Sapotaceae (Eberhardtia sp.),

Ulmaceae (Gironniera subaequalis).

A rare tree subendemic to Vietnam - Platanus kerrii (Platanaceae) sometimes appears as occasional dominant of canopy stratum in small remnants of gallery forests at lowest elevations in the area at about 300 m a.s.l.. These last forest remnants, which still survive along rivers in few places of the area, give us bleak approximate vision on primary lowland valley vegetation, which became extinct here many decades ago.

At elevations over 1400 m a.s.l., in lower montane and upper montane forests warm loving trees give way to representatives of families, which are more typical to subtropical and temperate Asia. Main dominants of highest forest strata in these woods belong to another group of families. Among them are:

Aceraceae (Acer laurinum, Acer spp.),

Betulaceae (Carpinus sp.),

Cupressaceae (Fokienia hodginsii),

Ericaceae (Rhododendron basilicum, R. cyanocarpum, Rhododendron spp.), Fagaceae (Castanopsis tonkinensis, Lithocarpus kunstleri, L. laotica, L. truncatus, Lithocarpus spp., Quercus annulata, Quercus spp.),

Hamamelidaceae (Exbucklandia populnea, Rhodoleia championii),

Illiciaceae (Illicium majus, I. petelotii, I. tsaii),

Lauraceae (Litsea spp.),

Magnoliaceae (Liriodendron chinense, Michelia spp.),

Rhoipteleaceae (Rhoiptelea chiliantha),

Rosaceae (Sorbus spp.),

Styracaceae (Rehderodendron macrocarpum, Styrax spp.),

Symplocaceae (Symplocos spp.),

Taxodiaceae (Taiwania cryptomerioides),

Theaceae (Anneslea fragrans, Schima wallichii, Schima sp.).

On tops of mountains at elevation over 2200 m, main dominants of dwarf elfin forests are numerous ericaceous trees and shrubs. Among them may be seen many species of Rhododendron, Pieris, Vaccinium and Enkianthus. Common dominants of montane forests (Illicium tsaii, Rhodoleia championii, Schima wallichii, Sorbus sp., Symplocos sp.) occur here as regular associated species. Many shrubs and trees in these habitats are deciduous. As a result, upper mountain vegetation during winter season bears certain resemblance with temperate Asian floras. This resemblance is underlined by numerous floristic elements connected in their distribution with montane and temperate Asia. Among them are species of such genera as:

Acer, Daphne, Lysimachia, Primula,

Acorus, Dichocarpum, Paris, Ranunculus,

Actinidia, Diplazium, Pedicularis, Sedum,

Asarum, Disporum, Platanthera, Sorbus,

Astilbe, Dryopteris, Pleione, Swertia,

Aucuba, Eleocharis, Fragaria, Viola.

Carex, Gentiana, Polypodium,

Carpinus, Lonicera, Polystichum,

Some of these species, like Astilbe rivularis, Fragaria nilagirica, Lysimachia laxa, Paris delavayi, P. polyphylla and Viola spp. are quite common at elevations higher than 1800-1900 m a.s.l. They form integral herbaceous element of the primary plant communities, both in close woody formations, and in more or less open habitats on steep montane slopes.

Specific secondary forests were observed in pristine conditions of the studied highland area on numerous rockslides and soil slips, as well as on enough wet stream slopes after forest fire. These rather open woods are composed on high elevations mainly with fast growing deciduous aboriginal trees like Carpinus sp., Liriodendron chinense, Styrax sp. and Rhoiptelea chiliantha. Among evergreen trees here also common Litsea spp. and Rhodoleia championii.

Secondary forests have still limited distribution at high elevations in the studied area. Main role in the formation of the characteristical landscape face of Lang Cung Mountains belong to majestic ancient relictual coniferous forests comprised of Fokienia hodginsii.

According to florogenetic composition, the flora of Lang Cung Mountains has closest similarity with montane flora of south-eastern Himalayas. Thus, the largest part (about 35%) of orchids discovered in mountain forests of Van Ban District has clear Himalayan connections. Among such orchids are:

Acanthephippium striatum, Agrostophyllum brevipes, Anoectochilus elwesii,

A. roxburghii,

Apostasia wallichii, Appendicula hexandra,

Bulbophyllum hymenanthum,

B. penicillium,

Calanthe herbacea, Cephalantheropsis obcordata, Ceratostylis himalaica, Coelogyne fimbriata,

Collabium assamicum, Dendrobium longicornu,

D. nobile,

D. thyrsiflorum,

Eria pannea,

E. pusilla,

Erythrodes blumei, Galeola nudifolia, Goodyera foliosa, G.fumata,

G. schlechtendaliana,

Liparis paradoxa, Mischobulbum cordifolium, Monomeria barbata, Panisea tricallosa,

Phaius mishmensis,

Pholidota chinensis, Platanthera angustata, Tainia viridifusca, Zeuxine nervosa.

Relatively few species of the flora have distinct connections with floras of southern part of Indochinese Peninsula and Malesia. Among orchids of such relations in Lang Cung montane flora are Calanthe densiflora, C. lyroglossa, Callostylis rigida, Eria amica, E. siamensis, Goodyera viridiflora, Hetaeria biloba, Leca-norchis javanica, Trichotosia microphylla and Vrydagzynea albida (totally less than 11% of discovered orchid species).

Considerable number of species observed in the flora of Lang Cung Mountains has wide distribution in tropical Asia. Within Orchidaceae this group represents about 35% of discovered species.

Vietnamese endemic and sub-endemic species having very strict distribution form large and very important integral part of the flora. This group of species outlines deep specificity of the flora and high level of its endemism. Among orchids the following species belong to this group:

Biermannia calcarata, Bulbophyllum atrosanguineum,

B. bisetoides,

B. insulsum,

Calanthe aleizettii,

Ceratostylis pygmaea,

Coelogyne lockii,

Cymbidium floribundum, Didymoplexiopsis khiriwongensis, Diglyphosa evrardii,

Epigeneium chapaense,

Eria gagnepainii,

E. thao,

Liparis chapaensis, L. petelotii,

Pleione grandiflora, Rhomboda petelotii.

This group represents about 19% species of the family Orchidaceae in the flora of the region. Among the 7 species are endemics of Sikang-Yunnan floristic province (Coelogyne lockii, Cymbidium floribundum, Epigeneium chapaense, Eria gagnepainii, Liparis petelotii, Pleione grandiflora, Rhomboda petelotii). Another 9 species are strict Vietnamese endemics. They are Biermannia calcarata, Bulbophyllum atrosanguineum, B. insulsum, Calanthe aleizettii, Ceratostylis pygmaea, Diglyphosa evrardii, Eria thao and Liparis chapaensis. Some sub-endemic species, like Didymoplexiopsis khiriwongensis and Bulbophyllum bisetoides have Indochinese range occurring beside Viet Nam in northern Thailand.

A number of species in the flora of Van Ban area appear as distinct geographical markers, which outline southern border of Sikang-Yunnan floristic province. Among them are:

Ainsliaea reflexa, I. tsaii, Taiwania cryptomerioides,

Angiopteris somae, Liriodendron chinense, Tsuga chinensis,

Asplenium laciniatum, Plagiogyria yunnanensis, Vernonia sylvatica.

Huperzia cancellata, Pleione grandiflora,

Illicium petelotii, Rhoiptelea chiliantha,

According to basic species composition, the flora of Lang Cung Mountains is typical of montane flora in northern part of Indochinese Peninsula. It represents relictual derivative of ancient Tertiary flora that once occupied wide tropical and subtropical areas of Europe, Asia and North America approximately 40-70 million years ago. Due to subsequent climate cooling and increased aridity this humid warm-loving flora was shifted during Coenozoic age to South-East Asia. Lang Cung Mountain flora like other montane floras of Indochina is typical variant of floras of such genesis. It exhibits surprisingly large proportion of archaic genera well represented in available fossils record of the Upper Cretaceous and Lower Tertiary, recorded from Europe, East Asia and North America (Kubitzki, Krutzsch, 1998; Martinetto, 1998; Averyanov, Nguyen Tien Hiep, 2002). Among them are numerous species of such families as:

Actinidiaceae (Actinidia petelotii, Actinidia spp.),

Annonaceae (Dasymaschalon rostratum, Desmos sp., Fissistigma balansae, Miliusa sp., Polyalthia sp.),

Betulaceae (Carpinus sp.),

Cephalotaxaceae (Amentotaxus argotaenia),

Cupressaceae (Fokienia hodginsii),

Fagaceae (Castanopsis tonkinensis, Lithocarpus kunstleri, L. laotica, L. truncatus, Lithocarpus spp., Quercus annulata, Quercus spp.),

Hamamelidaceae (Exbucklandia populnea, Rhodoleia championii), Lardizabalaceae (Stauntonia sp.),

Lauraceae (Actinodaphne sp., Cinnamomum sp., Cryptocarya sp., Litsea spp.), Magnoliaceae (Liriodendron chinense, Magnolia sp., Manglietia sp., Michelia spp., Paramichelia sp.),

Pinaceae (Tsuga chinensis),

Platanaceae (Platanus kerrii),

Podocarpaceae (Dacrycarpus imbricatus, Podocarpus neriifolius), Ranunculaceae (Dichocarpum sp., Ranunculus spp.),

Rhoipteleaceae (Rhoiptelea chiliantha),

Sabiaceae (Meliosma lepidota, Sabia parviflora),

Taxodiaceae (Taiwania cryptomerioides),

Theaceae (Anneslea fragrans, Schima wallichii).

Among mentioned families, the family Rhoipteleaceae is subendemic to the area. It is remarkable that its only representative Rhoiptelea chiliantha is common integral component of montane forests in uplands of Lang Cung mountain system. Another subendemic family here is Petrosaviaceae. It includes in the flora one species -Petrosavia sinii. This small achlorophyllous mycotrophic herb common in highland woods exhibits the most primitive gynoecium known in monocots.

In respect of its origin and taxonomic composition, the flora of Lang Cung Mountains represents uncial remnant relictual formation, which may serve as a model for the study of extinct forest floras and vegetation types widely distributed in Northern

Hemisphere during Tertiary age. This area of South-East Asia may be the birthplace and cradle of the Holarctic and even Paleotropic flora (Wu Z.Y. & Wu S.G., 1998). Discovery during the first reconnaissance explorations of highland flora of Lang Cung Mountains of some species new to the flora of Viet Nam (Ainsliaea reflexa, Begonia grandis, Bulbophyllum penicillium, Ranunculus nephelogenes, Vernonia sylvatica) and new species for science (Bulbophyllum atrosanguineum, Cheilanthes sp. nov., Sedum vietnamense) designates this flora as very rich but still poorly investigated.

Conservation

Despite proposed conservation status, the forests of Van Ban highland area are presently under serious press of uncontrolled exploitation by the local people community. Timber, medicinal and ornamental plants are main objects of commercial interests of local and international trade, which stimulate illegal exploitation of the natural resources of the area.

The large trees, timber of which are still widely explored in the area for building construction and sale, include Castanopsis spp., Fokienia hodginsii, Hopea mollissi-ma, Lithocarpus spp., Madhuca pasquieri and Michelia spp. Among medicinal plants, commonly collected for export as traditional oriental drags in Lang Cung Mountains, are such orchids as Anoectochilus elwesii, A. roxburghii, Goodyera foliosa, Hetaeria biloba, Platanthera angustata, Rhomboda petelotii, Spiranthes sinensis and different species of Dendrobium. Here occur also many other plants, locally used in primitive medicine of national minorities and in traditional oriental medicine. Among such species are:

Actinidia sp., Ardisia spp., Aristolochia sp., Asarum glabrum, Ilex sp.,

Illicium majus,

I. petelotii,

I. tsaii,

Kadsura coccinea, Paris delavayi,

P. polyphylla, Pedicularis sp.,

Schefflera sp., Strychnos sp.,

Tacca plantaginea, Viscum articulatum.

Among indigenous plants of Lang Cung Mountains having great potential for ornamental horticulture are numerous orchids, such as Calanthe aleizettii, Cymbidium floribundum, C. ensifolium, C. lancifolium, Dendrobium aduncum, D. brymeria-num, D. chrysanthum, D. longicornu, D. nobile, D. thyrsiflorum, Diplomeris pul-chella, Mischobulbum cordifolium, Pholidota articulata, Ph. chinensis and Pleione grandiflora, as well as representatives of many other angiosperms families. Among them are species of such genera as:

Actinidia, Astilbe, Disporum,

Aeschynanthus, Aucuba, Dracaena,

Aglaonema, Begonia, Enkianthus,

Amorphophallus, Crawfurdia, Gentiana,

Arisaema, Curculigo, Hedera,

Hoya,

Hupperzia,

Ixora,

Liriodendron,

Lonicera,

Mondapsis,

Ophiopogon,

Peliosanthes,

Peperomia,

Piper,

Pieris,

Polygonatum,

Rhododendron,

Schefflera,

Sedum,

Streptolirion,

Tupistra,

Vaccinium,

Viola.

Numerous ferns and some palms, like Licuala ternata and. Livistona sp. common in uplands of Van Ban District also belong to this group of potential ornamental plants.

Taking into consideration the current levels of local exploration, threat of extinction due to habitat destruction and general species rarity in the territory of Viet Nam, some species of the Lang Cung flora deserve status of IUCN categories of high threat (IUCN, 1994). According to our preliminary observations, these species may be classified as follows:

CR (critically endangered): Taiwania cryptomerioides.

EN (endangered): Fokienia hodginsii, Tsuga chinensis.9

VU (vulnerable): Amentotaxus argotaenia, Anoectochilus elwesii, A. roxburghii, Cymbidium ensifolium, C. floribundum, Dendrobium aduncum, D. brymerianum,

D. chrysanthum, D. longicornu, D. nobile, D. thyrsiflorum, Diplomeris pulchella, Fokienia hodginsii, Lecanorchis javanica, Madhuca pasquieri, Pleione grandiflora, Rhomboda petelotii.

Other plant species of Van Ban highland area may now be placed according to available data under LR (lower risk), DD (deficit data) and NE (not evaluated) categories. Detailed studies of their status in the flora are the subject of further field botanical investigations.

Field and laboratory studies, the results of which are presented in this paper, were funded by Fauna & Flora International (FFI-Vietnam Program) “Community-based Conservation of the Hoang Lien Mountain Ecosystem, Vietnam ”) and the American Orchid Society (“Population studies of endemic Paphiopedilum species in northern Viet Nam”). We would like to express also our great thanks to Mr. Steven Swan of FFI-Vietnam for his outstanding help during our field work and excellent outline of paths and trails in wild mountain woodlands of explored area. We also thank Dr. Jacinto Regalado of the Missouri Botanical Garden for his kind correction of our use of English language.

9 This status is applied not only to the species, but also to the forest stands composed with ripe samples of Fokienia hodginsii and Tsuga chinensis, which represent unique relictual plant formations one of the oldest and most endangered on our planet.

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РЕЗЮМЕ

Краткий предварительный обзор флоры и растительности горной системы Ланг Кунг, лежащей на юге района Ван Бан, провинции Лао Кай в северном Вьетнаме, проведен на основе оригинальных данных, собранных при проведении экспедиционных полевых работ в течение 2001-2002 годов. Описание растительности и анализ флоры основан на изучении модельных площадок и обширном гербарии, отражающем таксономический состав всех местообитаний, характерных для изучаемого региона. Сомкнутые вечнозеленые тропические муссонные (сезонно-влажные) леса являются главным типом растительности в изученной области. Они подразделены на низкогорные, предгорные, среднегорные и высокогорные леса. Последние два типа лесов, наиболее полно сохранившие свой первичный облик, описываются в работе с особой детальностью. Характер растительности

и систематический состав флоры гор Ланг Кунг типичен для южной оконечности высокогорий Сиканг-Юньнанской флористической провинции, представленных во Вьетнаме хребтом Хоанг Лиен Шон. Эта флора представляет производное древней третичной флоры Евразии и включает очень большое число архаичных родов, богато представленных в верхнемеловых и раннетретичных флорах Европы и Восточной Азии. По своему составу и происхождению эта флора представляет уникальное реликтовое образование, которое может служить своеобразной моделью для реконструкции биотических условий, характерных для северного полушария, существовавших в третичное время.

Ботанический институт им. В.Л. Комарова РАН г. С-Петербург

Получено 07.07.2003 г.