Hai loài mới Schizostachyum yalyense và S. ninhthuanense sp. nov. (họ Lúa: phân họ Tre) ở Việt Nam

The genus Schizostachyum was established by Nees von Esenbeck (1829) with a single species S. blumei Nees from Java. Since then, several authors have studied the genus taxonomically, and more than 50 species are currently recognized. They are distributed in tropical and subtropical Asia, from southern China to Malesia, extending to the Pacific Islands, with the majority of the species found in Malaysia and Indonesia (Dransfield 1983, Xia 1993, 1996, Ohrnberger 1999, Xia and Stapleton 2006). All species of Schizostachyum have sympodially branching rhizomes; erect or straggling thin-walled culms; branches of the same size arising from the node; spiklets in groups at the distal nodes of a branch base on leafy or wholly leafless branches; 1 to several bracts and no true glumes at bract base where they are joined onto the rachilla; lodicules may be present or absent (Holttum 1958, Xia and Stapleton 2006). During a survey on Schizostachyum in the Ninh Thuan and Gia Lai Provinces of southern Vietnam we collected specimens of a peculiar, flowering bamboo species. After having examined the specimens and consulted the relevant literature (Merrill 1916, McClure 1935, 1940, Dransfield and Widjaja 1995), we found that they were similar to Schizostachyum hainanense Merrill and S. lima (Blanco) Merrill in certain characters, but differed in other characters. They are described as a new species here.

Schizostachyum yalyense N. H. Xia, V. T. Tran et H. N. Nguyen

Type

Vietnam, Gia Lai Province, Yaly River, elevation 642 m a.s.l., 14809?010ƒN, 107853?372ƒE, Jul 2005, H. N. Nguyen, V. T. Tran (holotype: FSIV 06200504662, isotype: IBSC 0620050466).

Schizostachyum yalyense N. H. Xia, V. T. Tran et H. N. Nguyen

Schizostachyum yalyense

Distribution, habitat, and phenology

Schizostachyum yalyense is only known from the type locality in the northern highland of Vietnam, but found in several populations there. It grows in degraded natural forest valleys and mountain gorges, being common along rivers or valleys, between 400 and 700 m a.s.l. The species grows together with Dipterocarpus obtusifolius, Dalbergia tonkiensis, Irvingia malavana, Syzygium sp. etc. They were mass-flowering in 2005. The flowering period extends from Jun_Aug, and new shoots are developed at the same time.

Local uses and etymology

Schizostachyum yalyense is of considerable importance to the local people. Its culms are used for making handicrafts, household tools and tightening rice cakes which are very popular during the lunar New Year. The specific epithet refers to the type locality, Yaly River of Gia Lai Province, Vietnam.

Similar species

Schizostachyum yalyense is similar to S. lima (Blanco) Merrill in general appearance, but is distinct from it by its culm sheaths apically concave and 1.0_1.5 cm deep, and a single lodicule.

Schizostachyum ninhthuanense N. H. Xia, V. T. Tran et H. N. Nguyen

Type

Vietnam, Ninh Thuan Province, Ninh Son District, Ngoan muc Pass, elevation 962 m a.s.l., 11850?503ƒN, 108839?319ƒE, 15 Dec 2008, H. N. Nguyen, V. T. Tran (holotype: FSIV 1512200804661, isotype: IBSC 151220080466).

Schizostachyum ninhthuanense N. H. Xia, V. T. Tran et H. N. Nguyen

Schizostachyum ninhthuanense

Distribution, habitat and phenology

Schizostachyum ninhthuanense is only known from the type locality in the south centre of Vietnam, but found in several populations there. It occurs in degraded natural forest valleys and is common in mountain gorges, between 300 and 1000 m a.s.l. The species grows with Dipterocarpus intricatus, Dalbergia bariensis and Castanopsis pyriformis. It flowered from 2005 to 2008 with mass-flowering in 2006.

The flowering period extends from Aug_Dec and fruits are found Oct_Feb. New shoots are developed in Jul_Sep.

Local uses and etymology

Schizostachyum ninhthuanense is of considerable importance to local people. Its culms are used for making handicrafts, household tools and tightening rice cakes which are very popular in the lunar New Year. The specific epithet refers to the type locality, Ninh Thuan Province, Vietnam.

Similar species

Schizostachyum ninhthuanense is similar to S. hainanense Merrill ex McClure in general appearance, but differs by having a culm sheath apex with white_brown hairs, the ligule margins being densely pale-ciliate and densely covered with appressed white hairs on the dorsal surface, the lower surface of the leaf densely hairy and margins serrulate, two stigmas apically on the style and the third stigma branching off from one of the two other stigmas.

V. T. Tran and N.-H. Xia
H. N. Nguyen