Saturday 24 December 2022

Quercus mangdenensis: A new species of Oak from Vietnam.

Oaks, Quercus spp., are a large and diverse group of deciduous and evergreen trees, found throughout the temperate woodlands of the Northern Hemisphere, and extending south into subtropical and even tropical areas in some areas. In Southeast Asia they form a significant component of tropical montane forests, with 52 species known from Vietnam alone, seven of which were described as new species within the past five years, suggesting that the diversity of the group in this area is still not fully understood.

In a paper published in the journal Phytokeys on 15 December 2022, Nguyen Van Ngoc and Hoang Thi Binh of the Faculty of Biology at Dalat University, describe a new species of Oak from Kon Tum Province, Vietnam.

The new Oak was discovered while carrying out fieldwork around the town of Mang Den in Kon Plong District, at the northern end of the Central Highlands of Vietnam. The area has a cool tropical climate, with average temperatures varying between about 18.7 and 24.9°C over the course of the year, and a rainy season which lasts from August to February.

Type locality of Quercus mangdenensis. (A) Map of Vietnam. (B) Map of Kon Tum Province. (C) map of Kon Plong District, the red star indicated the type locality: Mang Den Town, Dak Long Commune. Ngoc & Binh (2022).

The new species is named Quercus mangdenensis, where 'mangdenensis' means 'from Mang Den'. It is an evergreen tree reaching 20-25 m high, with a trunk diameter of 60-80 cm. Leaves are lance-shaped with entire margins, and darker above than below. Bark is pale grey, except on the newest twigs, where it is green. Acorns are large, reaching 6-10.5 cm high and 4-5 cm wide. 

Quercus mangdenensis. (A) Twigs with young fruit. (B) Terminal buds. (C) Infructescences. (D) Fallen mature fruit. (E), (F) Adaxial and abaxial surface of the leaves. (G) Nuts. (H) Outside of cupule. (I) Densely reddish hairs inside of cupules. (J) Basal scar of the nut. (K), (L) Inside and outside of bud scale. Ngoc & Binh (2022).

Ngoc and Binh were able to find five subpopulations of Quercus mangdenensis, all growing at between 1050 and 1200 m above sealevel in fragmented evergreen forest. The area is under pressure from logging, farming and other Human activities, with the majority of the trees belonging to the new species on the border between forest clumps and farmland. For this reason Ngoc and Binh recommend that Quercus mangdenensis be classified as Critically Endangered under the terms of the International Union for the Conservation of Nature's Red List of Threatened Species.

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