THAI FOR. BULL. (BOT.) 39: 120–139. 2011.

The floodplain vegetation of the Trang River basin, peninsular : the threatened remnants of the freshwater swamp vegetation

PONLAWAT PATTARAKULPISUTTI* & KITICHATE SRIDITH*

ABSTRACT. The study of the scattered remnants of the floodplain vegetation in the Trang River basin, peninsular Thailand was carried out from November 2008 to January 2010. One hundred and sixty of vascular were recorded. The five most common families were Cyperaceae (22 species), Poaceae (12 species), (10 species), Fabaceae and (9 species each). Based on floristic compositions, nine association types were described. The spatial variation and differences in habitat distribution among these associations are explained by differences in successional stages due to the history of land uses and water regime. Moreover, the expected vegetation of the floodplain areas, reconstructed from the existing remnants left as isolated fragmentations, was proposed.

KEY WORDS: Floodplain vegetation, peninsular Thailand.

INTRODUCTION In spite of its biological importance there is scarce information on the species composition Floodplains are flat lands adjacent to streams of the floodplain areas in peninsular Thailand. or rivers, subjected to periodic flooding (Finlayson Besides, the floodplain vegetation in peninsular & Moser, 1991). Due to this periodic flooding, Thailand is among the most threatened habitats as plant species inhabiting these environments need it is subjected to human disturbances such as irrigation to have special modifications which enable either projects, agriculture, tourism, etc. Therefore, this tolerance of these changes, through physiology or study is aimed at giving an account of the floristic morphology, and/or avoidance through life history composition of plant communities in the floodplain traits (Capon, 2005). Thus, the floodplain areas are areas in peninsular Thailand. Remnant patches of unique and interesting habitats in terms of flora, floodplain vegetation are very interesting as all of plant morphological/physiological adaptations and them have never been inventoried. The study on vegetation structures, as well as vegetation dynamics. vegetation structure and floristic composition of this This floodplain vegetation, one of the least explored unique wetland vegetation of the floodplains along wetlands in Thailand, is not only botanically the Trang River basin, west coast of peninsular important, but also serves as an important habitat Thailand is thus necessarily and urgently needed for both terrestrial and aquatic fauna. before this vegetation disappears. Trang River is a short river (123 km length) near the west coast of peninsular Thailand. This MATERIAL AND METHODS river is interesting, because it is the only river in the western coast of peninsular Thailand that runs Study Area and Study Plots through a large basin. This basin is naturally flooded Field surveys were conducted in the floodplain annually. At the western coast of Thailand, floodplains areas of the Trang River, Trang province, located near are uncommon due to the generally steep gradient the west coast of peninsular Thailand (7º 30′ 13″– of the surface through which major rivers flow. A 7º 34′ 20″ N and 99º 31′ 40″ – 99º 35′ 40″ E). larger floodplain can be found along Trang River only.

* Prince of Songkla University Herbarium (PSU) & Centre for Biodiversity of Peninsular Thailand (CBIPT), Department of Biology, Faculty of Science, Prince of Songkla University, Hat Yai, Songkhla, Thailand, P.O. Box 90112. e-mail: [email protected] THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 121

The climate of the area is tropical monsoon (Am) channel. The most remote study plot is only around according to Köppen’s classification (Kottek et al., two kilometers distant from the river bank (Map 1). 2006) with a mean temperature of 27.4 °C and an This is not far enough to reach both the lateral average annual rainfall of 2,187.8 mm (during gradient as well as the flood gradient due to the 1961–1990). The heaviest rainfall is in September increased elevation from the main channel to the with average monthly rainfall of about 352 mm upland areas. Thus, the differences in depth, duration, (Thai Meteorological Department, 2010). The relative and frequency of the flood regime among the study humidity ranges from 62% in the dry season to sites vary due to the existing topographic relief 96% in wet season (Thai Marine Meteorological modified by human activities, i.e., landfills for Center, 2010). The mean annual runoff is 2,203.42 various agricultural purposes (oil palm and rice million m3 (during 2005–2009) and is the highest fields, etc.). during October to December and lowest during Fifteen study plots were selected within the January to April (Hydrology and Water Management remnant patches of the floodplain vegetation (Map Center of Southern Region, 2011). 1). The characteristics of each study plot are shown Since the drainage area of the Trang River in Table 1. Due to the lack of a proper hydrological basin is rather small and narrow, and almost all of station in the Trang River basin, the flood durations the floodplain vegetation has been modified by in the present study were estimated by field various human activities, only some isolated patches observations. of remnant vegetation have been left near the river

Map 1. The Trang River basin showing locations of the study plots. 122 THAI FOREST BULLETIN (BOTANY) 39

Data collection and vegetation classification to cover all seasons, fluctuations of rain-fall and inundation. All species within each Study plots were selected in accordance with study plot were recorded in order to make a com- the Braun-Branquet approach (Kent & Coker, 1994) plete species list. Abundance was measured by within the remnants of the “natural” floodplain cover-abundance estimation using the Domin-Krajina vegetation and inundation range from rarely to scale (Kent & Coker, 1994). Cluster analysis was permanently flooded (Table 1). In this case, according performed with PC-ORD software version 5.19 to van der Maarel (2005) the term “natural vegetation” (McCune & Mefford, 2006) using Euclidean distance means a system of largely spontaneous growing measure and Ward’s method (Ward, 1963) as have plants they can be both “primary” as well as “sec- been recommended by Kent & Coker (1994) in ondary” vegetations. Each selected plot was assumed order to classify the similar study plots into groups. as a representative area of a particular community Each of these groups would then be characterized type which is distinctly separated from the surround- as a given association type named in accordance ing vegetation in term of floristic composition and with the dominant species and physiognomy. structure. One 50 x 50 m plot, six 20 x 20 m plots and five 10 x 10 m plots were used as woodland plot Plant family classification of angiosperms (canopy > 15 m high), shrubland plots and grassland follows APGIII (Angiosperm Phylogeny Group, plots respectively, except for BR1R3, BR2R2 and 2009). Names of major clades within the angiosperms NT2R1 plots, which are scattered termite hills followed Simpson (2010). All voucher specimens and have an area of less than 5 x 5 m each. collected were deposited at Prince of Songkla University Herbarium (PSU). Data collection was carried out once a month from November 2008 to January 2010 in order

Table 1. Locations of study plots and their habitat characteristic along the Trang River floodplain.

Study plot Water Altitude Flood duration reference Map reference Site description depth (m) time number (cm)

BR1R1 N 7º 33′ 16″ E 99º 34′ 45″ 10 Old rice field Sept.–Nov. ca 30 BR1R2 N 7º 33′ 16″ E 99º 34′ 45″ 10 Old rice field April–Nov. ca 30 BR1R3 N 7º 33′ 16″ E 99º 34′ 45″ 10 Termite hills rarely BR2R1 N 7º 33′ 35″ E 99º 34′ 45″ 11 Old rice field Aug.–Nov. ca 30 BR2R2 N 7º 33′ 35″ E 99º 34′ 45″ 11 Termite hills rarely NT2R3 N 7º 35′ 06″ E 99º 35′ 20″ 12 Old rice field April–Nov. ca 30 KP1 N 7º 32′ 14″ E 99º 34′ 51″ 15 Disturbed forest Sept.–Nov ca 30 KP2 N 7º 32′ 11″ E 99º 37′ 52″ 15 Chopped Sept.–Nov. ca 30 KP3 N 7º 32′ 11″ E 99º 37′ 52″ 15 Primary Sept.–Nov. up to 100 vegetation KY1 N 7º 31′ 35″ E 99º 33′ 14″ 9 Old rice field Throughout up to 100 the year NT1R1 N 7º 34′ 57″ E 99º 35′ 10″ 14 Old rice field April–Nov. ca 30 NT1R2 N 7º 34′ 57″ E 99º 35′ 10″ 14 Old rice field Through year up to 100 NT1R3 N 7º 34′ 57″ E 99º 35′ 10″ 14 Disturbed forest rarely NT2R1 N 7º 35′ 06″ E 99º 35′ 20″ 12 Termite hills rarely NT2R2 N 7º 35′ 06″ E 99º 35′ 20″ 12 Old rice field Sept.–Nov. ca 30 THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 123

Relative abundance of life forms of association vines(v), epiphytes(e), geophytes(g), and herbs(h). types Likewise the annual plants were also subdivided into terrestrial and aquatic categories. The annual In order to explain spatial variation in com- terrestrial plant means the species which survive position and structure among association types flood period as seeds, while the category of annual based on vegetation classification, all vascular aquatic plant implies species which disappear in the plant species found on the Trang River floodplain dry period/or survive the long dry spell as seeds. were assigned to various growth strategies/life forms categories. This classification is based on the assumption that differences in plant morphology RESULTS AND DISCUSSION and life strategy would then reflect the different Plant diversity adaptation to various environmental conditions. Thus, if the dominant growth strategies/life forms A total of 160 species of vascular plants of each association type were investigated and belonging to 129 genera in 60 families are identified compared with the environmental factors such as and listed in Table 2. Among these, seven species history of land uses, flood duration and water are ferns and 153 species are angiosperms. The depth, these may help clarifying spatial variation most common families of are Rubiaceae among association types. (10 species, 6.25% of total flora), Fabaceae and Phyllanthaceae (9 species each, 5.6%) respectively. The abundance of each species of each com- Species belonging to Cyperaceae (22 species, 13.8 munity type was measured using its percentage %) and Poaceae (12 species, 7.5%) are among the cover of crown area. The relative abundance of most diverse group of Monocots. In this study, only each life form in each community type was then two species of Magnoliids were found. In the case calculated by summing the percentage cover of the of ferns, Pteridaceae (3 species, 1.9%) is the largest species in the same growth strategy/life form. family. Finally a relative abundance of growth strategies/ life-forms in each community type was expressed It is not surprising to witness the preponder- as percentage. ance of the largest families of Monocots mentioned in the floodplain vegetation. As regards to the Thai The plant species were divided into broad flora, Poaceae (600 species) and Cyperaceae (248 categories of annual and perennial. The former species) are also among the largest families (Office contains all vascular plant species which complete of the Forest Herbarium, 2011; Simpson & Koyama, their life-cycle within one year and survive the 1998). The elements of both Cyperaceae and unfavorable period as seeds. Some species which Poaceae are usually common in the floodplain or are usually regarded as perennial in other habitats freshwater swamp vegetation as many of them are were included in the annual category if in the both aquatic and terrestrial herbs. Concerning the floodplain they survive only one year. The peren- rest of plants beside the Monocots, the members of nial category, in this study, means all vascular plant family Phyllanthaceae are among the majority of species which live for more than one year, although pioneer plants in the scattered patches of shrubland some species may disappear during unfavorable associations (see Table 2). However, Rubiaceae periods but they remain their underground stems or and Fabaceae with several life forms and habits are rootstocks, i.e., rhizomes, corms. The perennial found in several types of associations as trees, plants were subdivided into terrestrial and aquatic shrubs and herbs. Thus, these families are the most ones. The aquatic plants are those who cannot live diverse in the floodplain vegetation. beyond wetland habitat for any significant period of time because most desiccate readily when The vegetation of the Trang River floodplain exposed to air (Tiner, 1991). The aquatic plants were divided, following Finlayson et al. (1989), into The Trang River floodplain vegetation was emergent(e), floating-leaved anchored(f), submerged classified into nine association types using the anchored(r), free floating submerged(b), and free Cluster analysis (Fig. 1). Naming of the association floating(d). The terrestrial plants were classified types were mainly based on physiognomy of the into trees(t), shrubs(s), woody climbers(w), dominant species. These association types were recognized as follows. 124 THAI FOREST BULLETIN (BOTANY) 39

- 3 Patt. 240 Patt. 565 Patt. 217 Patt. 458 Patt. 165 Patt. 471 Patt. 283 Patt. 562 Patt. 408 Patt. 219 Patt. 220 Patt. 224 Patt. 234 Patt. 181 Voucher Actinoscirpus 15 14 1 * 13 2 1 1 12 1 11 2 grassland); 4=NT1R2, 5=KY1( 2 1 10 9 * 1 8 2 3 2 1 1 7 2 1 2 1 2 1 6 1 2 Plots reference number 4 5 1 4 - - Streblus shrubland); 10=NT1R1, 11=KP2( shru 3 3 2 1 1 1 - Ziziphus Adenanthera shrubland). shrubland); 15 BR1R3 ( Streblus Pts Pts Pte Pte Ptv Ptv Ptv Ptv Pth Pth Ptv Ptv Ptv Pae Ath Aae Aae Life form (L.) Hook. (L.) M.G. Prince Decne. (L.) J. Sm. (Teijsm. & Binn.) (Teijsm. zeylanica (Burm. F.) Merr (Burm. F.) - Glochidion Mitragyna - Lagerstroemia (L.) R. Br. ex DC. sessilis (L.) R. Br. Scientific name indica religiosa grassland); 2=KP1( Paspalum - Cynodon ,- Hymenachene grassland); 3=BR1R2( Utricularia - Eriocaulon (Roxb.) Wall. ex Wight Wight ex Wall. Hoya parasitica (Roxb.) Drynaria quercifolia Alternanthera (Roxb.) G. Don Aganosma marginata Atherandra acutifolia sp. Taxocarpus Aitonr W.T. Ichnocarpus frutescens (L.) Tylophora piloselloides Pyrrosia Adiantum sp. L. aureum Acrostichum (L.) Brongn. Ceratopteris thalictroides Helminthostachys sp. Staurogyne (Cav.) R. Br. R. Br. (Cav.) microphyllum Lygodium tenuis Blume Tylophora Wrightia Kurz - Fimbristylis Family Aab = annual, aquatic Aad submerged; = annual, aquatic free Aaefloating; = annual, aquatic Ath emergent; = annual, terrestrial Atv herbs; = annual, terrestrial vines; Pa/tw = perennial, 1=NT2R3( Eleocharis No voucher is available for many plant species which were damaged during transportation or processing. Table 2. List of plant species in study plots. Abundance was measured by cover-abundance estimation using the Domin-Krajina scale. Abundance was measured by cover-abundance 2. List of plant species in study plots. Table Apocynaceae Polypodiaceae Amaranthaceae Apocynaceae Pteridaceae Ophioglossaceae Eudicots Ferns Lygodiaceae grassland); - Nauclea 6=KP3( - Lagerstroemia woodland); 7=NT1R3, 8=NT2R1, 9=BR2R2( bland); 12=NT2R2, 13=BR1R1, 14 BR2R1( aquatic/terrestrial woody climbers; Pae = perennial, aquatic emergent; Pag = aquatic/terrestrial woody perennial, aquatic climbers; geophytes; Pae Pas = perennial, = aquatic perennial, emergent; aquatic shrubs; Pa/ts = perennial, aquatic/terrestrial shrubs; Pa/tt perennial, = Ptv trees; terrestrial perennial, = Ptt shrubs; terrestrial perennial, = Pts herbs; terrestrial perennial, = Pth epiphytes; terrestrial perennial, = Pte trees; aquatic/terrestrial perennial, = terrestrial vines; Ptw = perennial, woody climbers. 1 2 3 THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 125 3 Patt. 236 Patt. 244 Patt. 401 Patt. 557 Patt. 178 Patt. 284 Patt. 453 Patt. 235 Patt. 268 Patt. 342 Patt. 350 Patt. 456 Patt. 461 Patt. 566 Patt. 197 Patt. 215 Patt. 567 Patt. 381 Patt. 374 Patt. 358 Patt. 337 Voucher 5 15 1 1 2 3 3 4 3 14 1 4 3 3 2 3 3 13 1 1 3 12 1 3 1 3 * 2 3 11 2 1 1 5 2 3 2 3 3 10 2 9 3 1 3 8 3 1 5 1 4 7 3 1 3 2 2 2 3 3 6 Plots reference number 1 5 1 4 3 3 4 3 2 1 1 3 2 1 1 tw tw Ptt Ptt Pts Pts Pts Pts Pts Pts Pts Pa/ Pa/ Pth Pas Pas Atv Atv Ath Ath Ptw Ptw Aae Aae Aae Life Pa/tt form Blume Vent. Vent. (L.) W.T.Aiton (L.) L. (Willd.) Esser (Willd.) Miq. (Wall.) Benth. (Wall.) L. indica pavonina L. Scientific name (Willd.) Merr. (Willd.) macrophylla strobilifera (Finet & Gagnep.) loureiri hookeri Pierre martinicensis (Jacq.) Choisy (L.) L. prostrata (L.) Willd. pennata (L.) Dillenia hirta (L.) Merr. Merremia Tetracera Aniseia calamansanai Rolfe Terminalia trifoliatum Cleome rutidosperma DC. Lobelia alsinoides Lam. indicum L. Heliotropium columnaris Santisuk Dolichandrone angustifolia Hydrocera Derris scandens (Roxb.) Benth. Derris sp Derris elliptica Flemingia Flemingia Sesbania javanica Eclipta caudatus Geiseler Croton Shirakiopsis indica Acacia Aeschynomene Adenanthera indica Pierre ex Craib Family Dilleniaceae Cleomaceae Boraginaceae Bignoniaceae Balsaminaceae Asteraceae Euphorbiaceae Fabaceae Drosearaceae 126 THAI FOREST BULLETIN (BOTANY) 39 3 Patt. 244-1 Patt. 362 Patt. 246 Patt. 194 Patt. 288 Patt. 373 Patt. 196 Patt. 260 Patt. 348 Patt. 176 Patt. 227 Patt. 241 Patt. 261 Patt. 223 Patt. 275 Patt. 344 Patt. 355 Patt. 239 Patt. 189 Patt. 167 Patt. 462 Voucher 8 3 15 8 2 14 4 4 3 2 2 13 3 4 3 12 6 2 2 3 11 2 1 3 1 2 10 7 3 9 7 1 7 2 8 7 4 3 3 8 4 1 5 4 * 7 2 4 2 3 1 2 4 8 7 2 6 3 3 5 Plots reference number 5 4 5 6 3 2 1 1 1 Ptt Ptt Ptt Ptt Ptt Pts Pts Pts Pts Pts Pts Pts Pts Pts Pts Pte Ath Ptw Ptw Aae Aae Aae Aae Aad Life form (Lour.) (Lour.) L. (Lour.) Corner (Lour.) L. L. L. Benth. & Hook. f. (L.) Vahl (L.) Scientific name phoenicea corchorifolia glabrata R. Br. malabathricum L. floribunda Jack Lagerstroemia speciosa (L.) Pers. Lagerstroemia cochinchinensis Macrosolen Tiegh. Utricularia caerulea Utricularia bifida L. Utricularia auria Lour. (L.) Gaertn. Vitex zeylanica Hydrolea paniculatum Clerodendrum annulata H.R. Fletcher Premna Glossocarya linnaei perakensis Corner Streblus Melochia Olax scandens Roxb. Syzygium sp. hispida L.f. asper Lour. Streblus tomentosa Sm. Microcos Pentapetes Maclura cochinchinensis L. Sida rhombifolia lobata L. Urena Family Loranthaceae Lentibulariaceae Hydrophyllaceae Olacaceae Myrtaceae Moraceae THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 127 3 Patt. 218 Patt. 273 Patt. 438 Patt. 424 Patt. 183 Patt. 437 Patt. 193 Patt. 195 Patt. 272 Patt. 231 Patt. 228 Patt. 182 Patt. 409 Patt. 441 Patt. 180 Patt. 214 Patt. 269 Patt. 375 Patt. 174 Patt. 225 Patt. 221 Voucher 6 15 3 3 7 1 6 2 5 14 4 7 6 1 2 8 3 3 3 13 4 7 1 1 1 1 8 3 12 * 3 * 1 1 9 3 11 2 5 2 2 2 9 4 10 3 7 9 5 5 3 1 5 2 3 8 6 5 3 3 1 6 2 2 3 7 3 1 3 2 3 2 6 3 6 2 2 Plots reference number 2 2 5 3 4 3 3 3 5 2 2 * 2 1 1 Ptt Ptt Ptt Pts Pts Pts Pts Pts Pts Pts Pts Pts Pts Pts Pts Ptv Ath Ath Ath Aae Aae Aae Aae Life Pa/ts form Gaertn. Wall. ex Lindl. Wall. Poir. Kurz (Wall. ex G.Don) (Wall. (G. Don) Exell (R.Br.) Soják (R.Br.) (Jacq.) P.H.Raven (Jacq.) P.H.Raven (L.) Mill. (Burm.f.) C.E.C. (L.) L. (Hook.f.) Ridl. Miq. eurhynchum Scientific name reticulatus urinaria L. longiciliata rubrum Blume dasyoneura Korth. (Roxb. ex Willd.) Willd.) (Roxb. ex virosa orientalis sp. vitis-idaea Miq. rostratus Sauropus Salomonia Phyllanthus punctata Hymenocardia Glochidion Bridelia Flueggea Royle Fisch. Morinda elliptica Nauclea alata (Aubl.) DC. Borreria Hedyotis herbacea L. horridum Blume (Ridl.) Tirveng. Kailarsenia campanula (Ridl.) Ludwigia hyssopifolia Ludwigia octovalvis Meyna sp. Havil. Naravelia Ziziphus oenopolia Xanthophyllum attenuata Family Polygalaceae Phyllanthaceae Rubiaceae Onagraceae Ranunculaceae 128 THAI FOREST BULLETIN (BOTANY) 39 3 Patt. 411 Patt. 264 Patt. 405 Patt. 186 Patt. 563 Patt. 401 Patt. 508 Patt. 507 Patt. 372 Patt. 433 Patt. 388 Patt. 190 Patt. 285 Patt. 232 Patt. 245 Patt. 387 Patt. 472 Patt. 184 Patt. 204 Patt. 343 Patt. 173 Voucher Patt. 262 15 3 2 2 1 2 1 1 14 6 3 4 2 2 13 3 4 * 2 1 2 2 2 12 3 2 3 1 1 2 11 2 5 1 1 1 2 1 1 3 10 2 9 1 1 3 3 3 2 8 1 4 1 4 3 3 2 7 3 6 2 3 Plots reference number 8 2 2 5 1 1 4 1 10 2 3 3 3 2 3 2 4 2 1 1 2 1 3 3 2 1 1 1 1 Ptt Ptt Ptt Pts Pts Pth Pth Pth Pae Pae Pae Ath Ath Atv Pag Pag Aae Aae Aae Aae Aae Aae Life Ptw form (Lodd.) Blume (L.) Benn. & R.Br. Sw. ex Willd. ex Sw. Benth. (L.) D. Don ex Sweet (Colsm.) Pennell L. (L.f.) Goetgh. & grossus Scientific name cobbe (L.) Raeusch. tenellum foetida Uvaria rufa Blume Cyperus compactus Retz. Leea rubra Blume ex Spreng. Pouzolzia zeylanica Stylidium Actinoscirpus D.A.Simpson Cyperus babakan Steud. Lindernia ciliata Muell. Lindernia crustacea (L.) F. Limnophila laxa Benth. Limnophila erecta Lepisanthes rubiginosa (Roxb.) Leenh. nudiflora (L.) Brenan Murdannia Allophylus Cyanotis axillaris (Retz.) Tirveng. & Tirveng. uliginosa (Retz.) Tamilnadia Sastre Paederia Commelina diffusa Burm. f. Crinum amoenum Roxb. ex Ker Gawl. Litsea sp. Limnocharis flava (L.) Buchenau Thwaites Lasia spinosa (L.) flagelliforme Typhonium Family MAGNOLIIDS Annonaceae Vitaceae Urticaceae Stylidiaceae Cyperaceae Scrophulariaceae Sapindaceae Rubiaceae Commelinaceae Amaryllidaceae Lauraceae MONOCOTS Alismataceae Araceae THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 129 3 Patt. Patt. Patt. 436-2 449-2 449-1 Patt. 428 Patt. 406 Patt. 419 Patt. 485 Patt. 475 Patt. 175 Patt. 429 Patt. 403 Patt. 481 Patt. 499 Patt. 568 Patt. 422 Patt. 446 Patt. 423 Patt. 480 Patt. 483 Patt. 402 Patt. 454 Patt. 492 Voucher 15 2 3 2 2 2 2 14 3 3 1 1 13 2 2 2 2 12 2 3 11 2 3 3 3 1 2 2 2 10 9 8 1 7 6 Plots reference number 2 1 5 4 4 2 3 7 8 7 4 5 2 3 4 4 1 3 4 2 3 5 1 5 1 1 1 2 3 6 3 6 3 8 3 4 4 1 6 5 2 2 1 Ptv Pae Pae Pae Pae Pae Pae Pae Pae Ath Ath Ath Ath Aae Aae Aae Aae Aae Aae Aae Aae Aae Life form (R.Br.) Kunth (R.Br.) (Roxb.) Schult. (Rottb.) P.Beauv. (L.) Vahl (L.) Rottb. Roxb. (Lam.) Vahl umbellaris (Lam.) Scientific name Vahl acuminata Vahl schoenoides R.Br. tetragona R.Br. miliacea

xeranthemum Mart. truncatum Buch.-Ham. ex acutangula brevifolia poiformis Retz. Fimbristylis Fimbristylis Fimbristylis Eleocharis Fimbristylis Fimbristylis Cyperus imbricatus Retz. Willd. ex Kunth Willd. Cyperus pulcherrimus Vahl Vahl Cyperus pilosus Cyperus digitatus Cyperus elatus L. Cyperus haspan L. Eriocaulon Eriocaulon Mart. sp. Dioscorea Kyllinga Lipocarpha microcephala (Retz.) T.Koyama T.Koyama flavidus (Retz.) Pycreus polystachyos Pycreus Makino Rhynchospora rubra (Lour.) Scleria Rhynchospora corymbosa (L.) Britton Family Cyperaceae Eriocaulaceae Dioscoreaceae 130 THAI FOREST BULLETIN (BOTANY) 39 3 Patt. 385 Patt. 346 Patt. 489 Patt. 506 Patt. 447 Patt. 505 Patt. 426 Patt. 450 Patt. 226 Patt. 504 Patt. 188 Patt. 187 Patt. 354 Patt. 280 Patt. 233 Patt. 391 Patt. 469 Patt. 407 Patt. 445 Voucher 2 2 15 2 2 2 14 1 1 13 * 2 12 3 2 3 1 2 3 11 2 3 2 2 * 10 2 9 2 8 7 1 5 1 2 2 2 6 Plots reference number 3 2 5 2 4 5 3 7 * 5 2 2 5 8 3 5 2 4 5 2 2 * 2 3 1 1 Pte Pte Pte Pte Ptv Ptv Ptv Ptv Pae Ath Ath Ath Ath Ath Ath Ath Ath Ath Aae Aae Aae Aae Aae Aae Aae Aab Life form Ridl. (Steud.) (Burm.f.) C.Presl Roxb. Lindl. (L.) Pers. L. (L.) Chase colona (L.) Link Scientific name indica indica alismoides (L.) Pers. rufipogon Griff. Cynodon dactylon Aerides sp. Thrixspermum leucarachne Echinochloa sp. Eragrostis Sw. crumenatum Sw. Dendrobium pallida Micropera Isachne globosa Kuntze Ischaemum rugosum Salisb. Oryza Ottelia Schumannianthus dichotomus Gagnep. Hymenachne acutigluma Gilliland Gloriosa superba L. Flagellaria Xyris indica L. Willd. Xyris pauciflora Monochoria hastata Solms Monochoria vaginalis Smilax sp. Stemona sp. Panicum sp. P.J. Bergius Bergius Paspalum conjugatum P.J. L. Paspalum scrobiculatum Sacciolepis Paspalum longifolium Family Poaceae Orchidaceae Hydrocharitaceae Marantaceae Liliaceae Flagellariaceae Xyridaceae Pontederiaceae Smilacaceae Stemonaceae THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 131

Figure 1. Cluster analysis dendrogram based on similarity of plant species composition and their abundance among the study sites.

1. Actinoscirpus grassland (NT1R2 and KY1) 3. Eleocharis-Fimbristylis grassland (NT2R3) It could be found in the old rice fields which This is a herbaceous plant community, seem- are flooded permanently by up to 1 m deep water. A ingly dominated by annual species. It is found in strand flora is remarkably formed by the emergent the areas which are subjected to relatively longer aquatic herbs. The dominant species is Actinoscirpus period of inundation (up to 30 cm deep water) for grossus, which formed more or less pure stands in about nine months. During the wet season, the this association. Minor species are also interspersed association is dominated by many annual aquatic among many aquatic herbs: Acrostichum aureum, species, i.e., Fimbristylis miliacea, Hydrolea Lobelia alsinoides, Ludwigia octovalvis, Ottelia zeylanica, Hymenachne acutigluma. Perennial alismoides, Persicaria attenuata, etc. aquatic plants are also plentiful, e.g., Eleocharis acutangula, Fimbristylis umbellaris and Scleria 2.Utricularia-Eriocaulon grassland (BR1R2) poiformis, etc. During the dry period, the terrestrial In the areas which are inundated for eight annual herbs, e.g., Eragrostis sp., Isachne globosa, months by up to 30 cm deep water, the association Sacciolepis indica are increasingly abundant. is dominated by annual aquatic plants and some of 4. Paspalum-Cynodon-Hymenachene grassland which are usually found in the bog and nitrogen (KP1) deficient areas, e.g., Drosera indica, Eriocaulon truncatum, E. xeranthemum, Fimbristylis miliacea, In the seasonally flooded areas, which are F. schoenoides, Salomonia longiciliata, Stylidium inundated for three months, the seasonally dynamic tenellum, Utricularia bifida, U. caerulea. However, association is mainly composed of annual herbs. In in relatively dry areas, Fimbristylis acuminata is the dry period, the association is dominated by plentiful. In the dry season the wet grasslands annual terrestrial herbs, e.g., Borreria alata, seasonally dry out, and most plants above ground Cynodon dactylon, Kyllinga brevifolia, Panicum are entirely withered. sp., Paspalum conjugatum, P. longifolium. During 132 THAI FOREST BULLETIN (BOTANY) 39 flooded period, annual terrestrial herbs are replaced species is Mitragyna diversifolia which forms by annual aquatic plants, e.g., Persicaria attenuata, almost pure stands. The other components are Cyperus haspan, Cyperus pilosus and Hymenachne small shrubs such as Glochidion rubrum, Leea ru- acutigluma. bra, and include the seedlings and saplings of Barringtonia acutangula and some scandent spe- 5. Mitragyna shrubland (NT1R1, KP2) (Fig. 3) cies, e.g., . Epiphytes and The Mitragyna association is found in the climbers are rare. The existence of ground cover disturbed floodplain areas and old rice fields, where species is seasonally dynamic. It is composed inundation is evident for 3–8 months. This associa- mainly of perennial and annual sedges and grasses. tion is dominated by shrubs and small trees species. Many of them are also found in Eleocharis- The canopy is continuous, 2–13 to (rarely) 15 m Fimbristylis grassland. high and has no trace of layering. The dominant

Figure 2. Profile diagram of theBarringtonia -Lagerstroemia-Nauclea woodland 1,3= Combretum trifoliatum; 2,5,16,17,19–22,26,28–29= Barringtonia acutangula; 4,24–25,30–32= Nauclea orientalis; 6–7,9,12,18,23,27= Lagerstroemia speciosa; 8,11,13–14,33–35= Schumannianthus dichotomus; 10= Mitragyna diversifolia; 15= Xanthophyllum eurhynchum THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 133

6. Mitragyna-Lagerstroemia-Glochidion shrub- 7. Barringtonia-Lagerstroemia-Nauclea wood- land (NT2R2, BR1R1, BR2R1) (Fig. 4) land (KP3) (Fig. 2) This association seems to be an intermediate This association is composed mainly of tree between Lagerstroemia-Streblus-Ziziphus shrub- species occurring in the areas which would be land and Mitragyna shrubland. It is found on the more or less flooded for about three months. The old rice fields which are flooded for 3–8 months. association is two-storied. The upper layer is 15–20 The species composition is similar to those two m high with rather continuous crown canopies, former mentioned associations, but different in the consisting mostly of tree species, e.g., Barringtonia relative abundance (see Table 2). The dominant acutangula, Lagerstroemia speciosa and Nauclea species are Antidesma ghaesembilla, Glochidion orientalis. The lower layer is varying from 3–5 m rubrum, Lagerstroemia floribunda, Leea rubra, height with many shrubs such as Streblus asper, Mitragyna diversifolia, and Ziziphus oenopolia. Kailarsenia campanula and the saplings of B. acu- The ground cover composition varies from a plot tangula, etc. In the areas under the relatively dense with no ground cover to a plot where annual aquatic canopies of the upper layer, the ground cover is plants such as Cyperus haspan, Cyperus pulcher- scarce. Whilst in the areas with relatively open rimus, Fimbristylis miliacea, are dominant during upper layer, a pure stand of Schumannianthus inundation periods. During dry periods, those dichotomus are occurring as a majority together species are replaced by terrestrial herb species, e.g., with Combretum trifoliatum and also seedlings Paspalum longifolium and Cynodon dactylon, etc. of B. acutangula. The epiphytes and climbers are

Figure 3. Profile diagram of theMitragyna -Lagerstroemia-Glochidion shrubland 1,11= Barringtonia acutangula; 2,3,6–7,9,10,12–14,16–20,28–35,37,39,41= Mitragyna diversifolia; 4= Taminaldia uliginosa; 5,36= Leea rubra; 8,22= Lagerstroemia floribunda; 15,23,27,40,42= Glochidian rubrum; 21,26,38= Antidesma ghaesembilla; 24,25= Ziziphus oenoplia 134 THAI FOREST BULLETIN (BOTANY) 39 relatively rich in this association when compared Melastoma malabathricum, Microcos tomentosa, with other floodplain association types. The following Streblus asper and Ziziphus oenopolia. The ground species are found: Dendrobium crumenatum, cover is rather scarce, however, some species can Drynaria quercifolia, Hoya parasitica, Micropera be encountered, although in low abundance, e.g., pallida, Pyrrosia piloselloides. Helminthostachys zeylanica, Melochia corchorifo- lia, Typhonium flagelliforme etc. 8. Lagerstroemia-Streblus-Ziziphus shrubland (NT1R3, NT2R1, BR2R2) 9. Streblus-Ziziphus-Adenanthera shrubland (BR1R3) Along the fringe of the floodplain where inundation seldom occurs and on the termite hills This association type is found on the termite which are confined to the old semi-permanent hills in the floodplain areas and mainly composed flooded rice fields, the association is mainly composed of shrub species which usually found on other dry of shrub and tree species. These species are also areas. Only seven plant species are found, i.e., common in other dry-land vegetation types, e.g., Adenanthera pavonina, Gloriosa superba, Microcos Antidesma ghaesembilla, Lagerstroemia floribunda, tomentosa, Stemona sp., Streblus asper, Uvaria

Figure 4. Profile diagram of theMitragyna -Lagerstroemia-Glochidion shrubland 1,11= Barringtonia acutangula; 2,3,6–7,9,10,12–14,16–20,28–35,37,39,41= Mitragyna diversifolia; 4= Tamilnadia uliginosa; 5,36= Leea rubra; 8,22= Lagerstroemia floribunda; 15,23,27,40,42= Glochidion rubrum; 21,26,38= Antidesma ghaesembilla; 24,25= Ziziphus oenoplia THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 135 rufa and Ziziphus oenopolia. The mentioned occurs. Due to the alternation period of drying and association type of vegetation can also be considered inundation, the plants with annual life-form have as a part of Lagerstroemia-Streblus-Ziziphus shru- more advantage as it could complete their life cycle bland which is left fragmented on the termite hills prior to unfavorable periods (depending on whether in the floodplain areas as five of seven species they are aquatic or terrestrial species) and leave belong to the Lagerstroemia-Streblus-Ziziphus their seeds to establish in the next favorable season. shrubland. This trait also renders them to readily colonize the unoccupied land following a disturbance. Therefore Relative abundance of life forms and spatial this life-form is predominant in the areas with fre- variation in composition and structure among quent disturbances and unpredictable environment the association types of the Trang-River (see also Finlayson et al., 1989; Capon, 2005). floodplain vegetation 2. The association dominated by perennial herbs According to the nine association types clas- sified above, the relative abundance of life forms in The association dominated by perennial each association types are performed in percentage herbs is found in the disturbed and inundated areas in Table 3. Based on these data, the association all year round. They may be developing in the early types according to vegetation classification could stage of succession similar to the former one. be categorized into three main groups according to However, the difference in physical setting between the dominant life forms, i.e., (1) the association these two association types is the water regime. In dominated by annual herbs which are composed the Actinoscirpus grassland the soils never com- of Paspalum-Cynodon-Hymenachene grassland, pletely dry out even during the dry season, the con- Utricularia-Eriocaulon grassland, and Eleocharis- dition which is suitable for aquatic plant species. Fimbristylis grassland; (2) The association dominated Due to the relatively stable environmental condition, by perennial herbs that is Actinoscirpus grassland; compared to the association dominated by annual (3) The association dominated by perennial woody herbs, the perennial aquatic plant species in this species which are composed of Mitragyna shrubland, association have enough time to complete their life Mitragyna-Lagerstroemia-Glochidion shrubland, cycle. Hence, in this condition the predominant Lagerstroemia-Streblus-Ziziphus shrubland, perennial species have more advantage over the Barringtonia-Lagerstroemia-Nauclea woodland annual herbs. This reveals the role of flood duration and Streblus-Ziziphus-Adenanthera shrubland. in differentiating the species composition and structure between these two association types. It is usually found that stands of the vegetations with completely different floristic composition 3. The association dominated by perennial may have similar structure and life form as a woody species consequence of an interaction of the complexity of This group is found in the varying habitats of similar environmental factors. Therefore, the semi-permanently flooded areas, the seasonally spatial variation within the floodplain vegetation of flooded areas and the infrequently flooded areas. Trang River is briefly discussed in accordance with However, only Barringtonia-Lagerstroemia- these three main groups as follows: Nauclea woodland is considered to be “primary 1. The association dominated by annual herbs vegetation”, which has long been existed in the study areas originally. It has relatively complex This group was found in the disturbed and structure, e.g., 2-layered canopy, dominated by larger inundated areas which last for 3–4 and 8 months. trees and rich in epiphytes compared with other According to Odum (1969), the small size of plants, types of association in the Trang River floodplain. the rapid rate of growth and the short life cycle are In any case, more information on the vegetation the characteristics of organisms in the early stage history is, therefore, needed in order to confirm this of succession. This may indicate that they are observation. developing in the early stage of succession. Moreover, it is noticeable that these associations However, in the disturbed floodplain areas, are found in the areas where seasonally inundation the associations of the Mitragyna shrubland and 136 THAI FOREST BULLETIN (BOTANY) 39

Table 3. Percentage cover of life forms in each association type along the Trang River floodplain.

Association types2 Life forms1 1 2 3 4 5 6 7 8 9

Aab 4 1 Aad 1 Annual herbs Aae 44 42 72 29 3 1 20 12 Ath 20 47 18 2 1 10 6 Atv 2 2 1 3 3 2

Pae 29 6 7 40 5 10 3 Pag 2 1 1 Perennial herbs Pte 9 1 1 Pth 5 5 3 9 1 3 2 Ptv 2 9 6 2 5 14

Pa/tw 5 1 Pas 7 1 Pa/ts 3 4 2 Woody species Pa/tt 3 Pts 29 48 28 39 76 Ptt 23 25 18 21 Ptw 7 5 9 2 8 10

1Aab = annual, aquatic submerged; Aad = annual, aquatic free floating; Aae = annual, aquatic emergent; Ath = annual, terrestrial herbs; Atv = annual, terrestrial vines; Pa/tw = perennial, aquatic/terrestrial woody climbers; Pae = perennial, aquatic emergent; Pag = perennial, aquatic geophytes; Pas = perennial, aquatic shrubs; Pa/ts = perennial, aquatic/terrestrial shrubs; Pa/tt = perennial, aquatic/terrestrial trees; Pte = peren- nial, terrestrial epiphytes; Pth = perennial, terrestrial herbs; Pts = perennial, terrestrial shrubs; Ptt = peren- nial, terrestrial trees; Ptv = perennial, terrestrial vines; Ptw = perennial, terrestrial woody climbers. 21= Eleocharis-Fimbristylis grassland, 2= Paspalum-Cynodon-Hymenachene grassland, 3= Utricularia- Eriocaulon grassland, 4= Actinoscirpus grassland, 5= Barringtonia-Lagerstroemia-Nauclea woodland, 6= Lagerstroemia-Streblus-Ziziphus shrubland, 7= Mitragyna shrubland, 8= Mitragyna-Lagerstroemia- Glochidion shrubland, 9= Streblus-Ziziphus-Adenanthera shrubland. THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 137 the Mitragyna-Lagerstroemia-Glochidion shrubland the association types except the Barringtonia- are found to replace of the Barringtonia- Lagerstroemia-Nauclea woodland may be repre- Lagerstroemia-Nauclea woodland. Noticeably, senting the transitional stages of succession. these shrubland communities share similar envi- Generally, floodplains are characterized by dynamic ronmental conditions with other associations of fluvial landforms and natural succession, which dominated by annual herbs. According to the is usually associated with a particular kind of veg- appropriate duration of the secondary successional etation (Tepley et al., 2004; Wittmann et al., 2004). stages, the small tree and shrub species could well Secondary succession of the existing associations establish themselves and dominate in the woody due to human activities in the floodplain vegetation vegetation, but not the annual species. Moreover, of the Trang River may reflect natural-successional most of the ground cover species commonly found course due to this dynamic of fluvial landforms in both the Mitragyna shrubland and the main com- along the lateral gradient. Based on these data of ponents of Eleocharis-Fimbristylis grassland may the natural-successional courses, the expected as- suggest that the Eleocharis-Fimbristylis grassland sociations of the floodplain vegetation of the Trang might has a potential to develop as the Mitragyna River basin are, therefore, proposed as follows. shrubland thereafter. In addition, the proliferation The succession process could be initiated on of the seedlings of Barringtonia acutangula in the the newly sedimentation site, e.g., the inner side of Mitragyna shrubland may suggest that this associa- a curve of the river, abandoned meanders or the tion would likely be replaced by the Barringtonia- oxbow lakes. The early stage of succession was Lagerstroemia-Nauclea woodland thereafter. This likely predominated by the herbaceous association. suggests that the differences in varying successional Either perennial or annual herbaceous associations stages due to the history of land uses in the study could be expected at varying water depth and the areas are responsible for the variations in floristic seasonal dynamic of water regime. These herbaceous composition, structure and distribution among the association would be able to trap the additional association types. sediment and, therefore, providing suitable habitats Considering distribution of Lagerstroemia- for the later colonizers. Then, these types of asso- Streblus-Ziziphus shrubland and the Streblus- ciation may be replaced by the Mitragyna- Ziziphus-Adenanthera shrubland, these associations Lagerstroemia-Glochidion shrubland or the exist in the infrequently flooded areas formed by Mitragyna shrubland. Eventually, the successional small mounds 1–2 m high, and scattered “termite process may end up with the Barringtonia- mounds”. According to this rarely flooded condition, Lagerstroemia-Nauclea woodland. However, the the Lagerstroemia-Streblus-Ziziphus shrubland and so-called climax vegetation may be repeatedly the Streblus-Ziziphus-Adenanthera shrubland are disturbed by the natural erosion process of the dominated by the terrestrial species (e.g., Microcos flood and then the succession would resume again. tomentosa, Streblus asper, Ziziphus oenopolia) Therefore, the varying association types along the which are common in some dry land habitats. lateral gradient in the natural floodplain may repre- sent different successional stages (Fig. 5b). Expected original association types in the Trang River basin However, as all remnant patches of the flood- plain vegetation have been left nearby the river The spatial variation and differences in habitat channel, the Barringtonia-Lagerstroemia-Nauclea distribution among the association types in the woodland seems to be the only primary type of the present study might be explained primarily by dif- typical freshwater swamp vegetation existed on ferent successional stages of secondary vegetation. this floodplain. Many more natural association Because most of the study sites were found on types could have occurred in the past, especially, areas disturbed by humans (see Table 1), the variation the association types located far apart from the among the association types along a lateral gradient river channel. The more intensive surveys in the seems to be the reflection of human disturbances similar floodplains in the peninsular Thailand are, rather than the natural processes (Fig. 5a). All of therefore, needed for a comparative study. 138 THAI FOREST BULLETIN (BOTANY) 39

Figure 5. Varying associations of floodplain vegetation along a lateral gradient from river channel to elevated areas in the Trang- River basin, between a) spatial variation as a result of secondary succession due to human impact in actual vegetation and b) the expected vegetation of floodplain along the lateral gradient due to natural succession (note that different association types become established in relation to flood-level gradient). 1= the association dominated by annual species and/or the association dominated by perennial herbs, 2= Mitragyna-Lagerstroemia- Glochidion and/or the Mitragyna shrubland, 3= Barringtonia-Lagerstroemia-Nauclea woodland, 4= Lagerstroemia-Streblus- Ziziphus shrubland.

Conservation measures have never been included in any protected area categories. Many of native plant species have The freshwater swamp or floodplain vegeta- already disappeared from their original wetland tion is not only important in terms of biodiversity habitats. Furthermore, most of the floodplain areas and genetic resources of many specialized flora in the river basins, the natural periodic flood has and fauna species, it provides also a number of recently not taken place anymore, and some areas non-timber forest products for local use and supports have altered to be permanently flooded due to the fisheries. So far, diverse vegetation types on the excessive irrigation systems. In the absence of floodplains and alluvial plains in every region of flood, the native plants of natural floodplains are Thailand have increasingly been threatened and consequently replaced by the species of dry habi- degraded by various agricultural activities, espe- tat. Whilst in the permanently flooded condition, cially rice fields, and para-rubber plantation. The the natural floodplain vegetation may change into loss of freshwater swamp vegetation includes the aquatic plant communities as in the open water (see permanent loss where the altered areas are no longer Middleton, 2002). If the natural water regime in possess wetland characteristics, or change from maintaining the natural floodplain vegetation natural to semi-natural or unnatural. Today, the would not be taken into account for the irrigation intensive and destructive land uses of this wetland projects managements as well as various agricul- ecosystem by people have reached a critical level ture activities together with the ignorance of the that only a few remnant patches of the natural authorities concerns and the local inhabitants, this freshwater swamp vegetation are left in the flood- rare habitat would then disappear soon from the plain areas of the Trang River basin. Unfortunately, former river basins, at least in peninsular Thailand. almost all the floodplain areas of Trang River basin THE FLOODPLAIN VEGETATION OF THE TRANG RIVER BASIN, PENINSULAR THAILAND: THE THREATENED REMNANTS OF THE FRESHWATER SWAMP VEGETATION (P. PATTARAKULPISUTTI & K. SRIDITH) 139

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