Orchids of Cuc Phuong National Park - lllustrated Guide (eBook)

CUC PHUONG NATIONAL PARK

BRIEF INFORMATION

GEOGRAPHY

Cuc Phuong National Park is the oldest national park in Vietnam. Established in 1960 as a protected area, two years later it was decreed the first national park in the country on 2 July 1962. The Cuc Phuong National Park is located about 100 km SSW of Hanoi. It lies between Hoa Binh, Ninh Binh and Thanh Hoa Provinces between 20°14' N and 20°24' N latitudes and between 105°29' E to 105°44' E longitudes. The Park covers about 222 sq km, three-quarters of which are low limestone hills and mountains with elevations ranging between 150 and 600 m above sea level. Administratively, Cuc Phuong National Park belongs to Ninh Binh (11350 ha), Hoa Binh (5850 ha) and Thanh Hoa Province (5000 ha). There is only one permanent river in the national park. This is Song Buoi River which bisects the western end of the Park from north-west to south-east, and feeds the Ma River, the major river in Thanh Hoa Province. There are also many small temporary streams during the rainy summer period, which, however, dry up in the winter dry season.

GEOLOGY

Geologically Cuc Phuong National Park area represents the remnants of the terminal decreasing easternmost part of a highly eroded ancient limestone plateau. Remnant mountains and hills here are composed of solid crystalline gray marble-like limestone, which represents relictual geologic formation derived from marine deposits of Triassic age accumulated more than 200 millions years ago (Dovzikov et al., 1965a, b). The main body of this limestone formation lies in the NW part of Vietnam in the territories of Hoa Binh, Lai Chau and Son La Province and is known as the Sin Ho (Ta Phin), Son La and Moc Chau plateaus elevated at their north-western extremity up to 1500–1700 m a.s.l. These plateaus extend along the Song Da (Black) River from the Chinese border in a SE direction to the coastal lowlands in the form of more or less narrow landscape bodies. A very deep karstic erosion of ancient limestone is very typical for these low uplands spreading on coastal plains. In these regions weathered highly eroded limestone formations yield spectacular topography with numerous isolated mesa-like remnants, low hills often with nearly vertical cliffs faces, numerous caves, and narrow rocky ridges dissected by deep river valleys filled with young alluvial material. Such landscape with predominant elevations of remnant rocky limestone hills between 300--500 m a.s.l. is characteristic for the territory of Cuc Phuong National Park. The rocky limestone ridges rise sharply out of the surrounding alluvial plains to peaks at elevations of 400--600 m. May Bac, the highest mountain of the national park, has a peak at 656 m a.s.l. The section of the rocky limestone in the national park comprises an oval-shaped area around 10 km wide and 25 km long with a central valley running along the entire massif. Sub-soils in the valleys comprise Triassic schist layers overlaid with secondary soils showing some signs of recent upheaval and intermixing. Occasional ferralitic deposits impart them with a reddish color. Top soils are partly red calcareous, with rendzina and sequential brown and nearly black soils on ridges. Forest soils are generally very shallow.

The exposed rocky limestone landscape provides the national park unique habitats of plant communities with numerous local endemics. It is a globally important example of a limestone karst ecosystem and the only remaining large area of lowland limestone forests in north-eastern Indochina.

CLIMATE

The climate of Cuc Phuong National Park is classified as monsoon tropical climate with a cool dry winter and summer rains (Nguyen Khanh Van et al., 2000). It is described on the basis of data available from the two nearest climate stations at Ninh Binh and Nho Quan towns (see map). Annual rain precipitation averages around 1800--1900 mm with mean annual temperatures 23.3--23.4 C. A hot damp summer with an abundance of torrential heavy rain from May-June until September-October is typical for the area. The winters are dry and rather cool from October to April. Average summer temperatures usually vary between 25--30 C and the usual winter temperatures hovers around 15--18 C (see diagram). An average annual temperature during the year is about 23.3--23.4 C. On the coldest winter nights, at elevations of 2--12 m, the temperatures may approach 2.4--5.7 C (absolute minimum detected). Cold foggy and misty weather during later February — early April is very typical for the area. Ambient humidity at this time is very high, particularly on hill slopes and ridge tops. Meanwhile most of the rain the area receives is quickly absorbed by a complex underground drainage system and the rocky slopes remain relatively dry throughout the year.

Climatological data for Cuc Phuong National Park area.

Black figures at the chart bottom are months. Blue axis represents atmosphere precipitation in mm (columns designate mean month rainfalls); red axis represents mean monthly temperature in ºC. The deep blue and deep red are data from the Nho Quan weather station, 20º19'N 105º44'E, elev. 12 m a.s.l.; light blue and light red are data from the Ninh Binh weather station, 20º16'N 105º59'E, elev. 2 m a.s.l. all according to Nguyen Khanh Van at al., 2000.

FLORA

The territory of Cuc Phuong National Park belongs to the area of the North-Indochinese floristic province according to modern phytogeographic division of the Indochinese Peninsula (Averyanov et al., 2003a,b). The modern flora of the Park has a distinctly heterogenic character including aboriginal and invasive elements. As in the majority of tropical floras, the role of invasive species in the flora permanently rises, whereas the aboriginal floristic nucleus slowly declines. Due to this process, the richness of the whole flora increases by means of fast naturalization of foreign weeds and introduced exotic species. According to a recent inventory (Soejarto et al., 2004) the whole flora of Cuc Phuong National Park includes about 2000 species of flowering plants in 887 genera and 221 families. The ten largest families in this flora are:

The aboriginal floristic nucleus of the national park flora is typical for other indigenous tropical lowland limestone floras of its floristic province. All orchids reported from the Park represent native aboriginal elements. This is the largest family in the nucleus of the native flora.

VEGETATION

Tropical evergreen broad-leaved lowland forests are the typical vegetation in lowland areas of this floristic province ( Fig. 1 ). Two variants of these forests - forests on rocky limestone and forests of flat alluvial valleys - are main kinds in the Park. Forests of both kinds in pristine condition are very species rich and have a complex vertical structure with a number of distinct strata. Due to karstic drainage, forest conditions on rocky slopes and particularly on ridges tops are much drier than in habitats along flat alluvial river valleys running between limestone ridges. The first stratum of primary forest here hardly reaches 20 m tall. In more wet conditions of valleys, shaded from strong winds, forest canopy dominants form a more or less continuous upper stratum at approximately 25–30 m high with occasional sporadic emergent trees up to 50 m high. Regular canopy dominants of primary valley forests in Cuc Phuong National Park are numerous warm loving representatives of such tropical families as

Anacardiaceae (Allospondias lakonensis, Dracontomelon duperreanum, Drymicarpus racemosus),

Annonaceae (Mitrephora maingayi, M. thorelii),

Burseraceae (Canarium album, C. bengalense, C. subulatum, C. tramdenum, Garuga pinnata),

Clusiaceae (Garcinia...