NE Thailand Research Articles

A new species, Hoya honglenae and the first report of H. acuminata and H. phuwuaensis (Apocynaceae, Asclepiadoideae) in the flora of Vietnam

Three species of the genus Hoya (Apocynaceae, Asclepiadoideae) are newly reported for the flora of Vietnam. One species, Hoya honglenae, is described and illustrated as new to science, and two species, H. acuminata and H. phuwuaensis, are reported as new national records known earlier, respectively, in Bhutan, Bangladesh, NE India, W China, Myanmar; and NE Thailand. The new species discovered in Phu Quoc Island (Kien Giang Province) morphologically is most close to H. phuwuaensis, but differs in the entire, straight leaf margin, leaves sparsely white speckled adaxially and dirty purple speckled abaxially, smaller yellow flowers, conoid, obtuse, distally up-cured outer angle of corona lobes, and much longer anther appendages. The paper provides morphological descriptions, data on habitat, phenology, distribution, estimated conservation status, taxonomic notes, a list of studied specimens, and color illustrations for all studied species. Taking into consideration our new data, the genus in Vietnam currently includes 44 species.

Effects of Tree Functional Traits on Soil Respiration in Tropical Forest Plantations

Fast-growing tree species, including Eucalyptus sp. and Acacia sp., are widely used to rehabilitate degraded tropical forestland quickly, while mitigating climate change. However, the extent of carbon losses through soil respiration (RS) often remains unknown. Moreover, the promotion of these non-native species has raised concerns over their impact on other ecosystem services, including N2-fixation-induced soil acidification and nutrient cycling. This study compared two non-native and native species, with one of each being N2-fixing, growing in 11-year-old monospecific plantations in NE Thailand. Hourly RS was measured monthly over one year and combined with stand characteristics, as well as soil microclimatic and chemical properties. Mixed-effects models were used to capture this hierarchical, diurnal, and seasonal dataset. RS rates were influenced by soil temperature and moisture following a parabolic relation, and negatively affected by acidity. Overall, RS varied significantly according to species-specific microclimates and productivity. Despite the high input of organic matter, non-native species failed to ameliorate extreme soil moisture or temperature; limiting microbial decomposition and reducing RS. Hopea odorata produced moderate levels of carbon sequestration, but maintained soil fertility. The choice of tree species can significantly affect carbon sequestration and storage, as well as nutrient cycling, and careful species selection could optimize these ecosystem services.

The First Fossil Coelacanth from Thailand

Mawsoniidae is a family of coelacanths restricted to the Mesozoic. During the Cretaceous, mawsoniids were mainly represented by the Mawsonia/Axelrodichthy complex, long known to be from western Gondwana only (South America and Africa). This apparent biogeographical distribution then faded following the discovery of representatives in the Late Cretaceous of Laurasia (Europe and North America). We report here the presence, in the Lower Cretaceous site of Kham Phok, NE Thailand, of an angular bone referred to the Mawsonia/Axelrodichthys complex. A comparison with angulars referring to both genera found in various regions of the world between the Late Jurassic and the Late Cretaceous indicated that the distinctions between these genera, and even more so between their constituent species, are unclear. This discovery is further confirmation of the very slow morphological evolution within this lineage, which may explain why their evolutionary history appears to be disconnected, at least in part, from their geographical distribution over time.

New material of turtles from the Upper Jurassic of Phu Noi, NE Thailand: Phylogenetic implications

New shell material of Phunoichelys thirakhupti and Kalasinemys prasarttongosothi are reported from their type locality, Phu Noi site, Khorat Plateau, NE Thailand. These new specimens complete our knowledge of their anatomy. Intraspecific and ontogenetic variations are observed in P. thirakhupti; and reconstruction of the shell is provided for both species. Both Phunoichelys and Kalasinemys are aquatic turtles, but their shell morphology is distinct, suggesting different mode of life. A phylogenetic scenario is presented where the previously character based Xinjiangchelyidae appear to be paraphyletic, suggesting more phylogenetically diverse lineages were present in Eastern and South-east Asia during the Jurassic.

How Do Sustainable Development-Induced Land Use Change and Climate Change Affect Water Balance? A Case Study of the Mun River Basin, NE Thailand

How Do Sustainable Development-Induced Land Use Change and Climate Change Affect Water Balance? A Case Study of the Mun River Basin, NE Thailand

Processes governing nutrient dynamics in tropical urban-agriculture rivers, NE Thailand

Processes governing nutrient dynamics in tropical urban-agriculture rivers, NE Thailand

Forecasting 100-year changes of streamflow in the Mun River Basin (NE Thailand) under the HAPPI experiment using the SWAT model

Abstract The Lower Mekong River is one of the significant rivers nurturing people on the Southeast Asian mainland. Its tributaries include the Mun River (NE Thailand), which often experiences extreme water events. In this study, the streamflow change in the year 2115 was simulated by relying on the Half a degree Additional warming, Prognosis and Projected Impacts (HAPPI) experiment and the Model for Interdisciplinary Research on Climate, version 5 (MIROC5) climate model for average global warming of 1.5 °C (Plus1.5) and 2.0 °C (Plus2.0) above pre-industrial levels and compared with the base year in 2015 for the Mun River Basin. The Soil–Water Assessment Tool (SWAT) was used for the streamflow simulation. The results showed an increasing air temperature against lowering rainfall and relative humidity (except for the post-monsoon months), suggesting overall rain suppression in response to the warming climate. The median projected annual streamflow to the Mekong River in 2115 decreased for both ‘Plus1.5’ (−32.5%, median) and ‘Plus2.0’ (−23.1%, median). However, increasing annual streamflow could be found only in the middle part. Seasonal streamflow changes revealed a different spatiotemporal response to climate change resulting in inconsistent streamflow changes across the basin. The adaptive measures for the middle part should be focused on flooding control, whereas the upper and the lower parts should be against drought.

Alteration of high alkaline and alkaline basaltic rocks: parent rocks in the Lava Durian orchard, Sisaket Province, NE Thailand

Lava Durian Sisaket is the first geographically identified (GI) fruit related to the volcano in Thailand and distributed in three districts of Sisaket Province, the southernmost edge of the Khorat Plateau. The parent rocks of orchards are important for the description of soil and rock relation with respect to mineralogical and geochemical characteristics. This work aims to study lithology, mineralogy, and geochemistry of basaltic rocks, parent rocks of in situ soil in these orchards, and delineate the existing basaltic soil models. The several orchards are covered by reddish-brown to brown in situ soils, weathered from mafic volcanic rocks: porphyritic olivine basalt, vesicular olivine basalt, and nephelinite. The microscopic image analysis, XRD, and MiniSEM-EDS are used to classify mineralogy, while XRF and analysis of large and rare elements in ICP-MS/ICP-OES were used to determine parental rocks geochemistry and alteration. The olivine basalts comprise forsterite microphenocrysts associated with bytownite, diopside, augite, pigeonite, and ilmenite groundmass, while nephelinite is composed of nepheline groundmass and bytownite-labradorite, diopside, augite, pigeonite, and ilmenite crystals. In addition, these basalts display high alteration rates, especially olivine highly altered to iddingsite. According to the geochemical data, Sisaket's basalts were identified as alkali basalt and nepheline basanite with high LILEs and LREEs (La, Nd, Pr, Gd, Eu). The kaolinite, smectite, and illite are altered from felsic minerals, while the chlorite and iddingsite are from mafic minerals. The mineralogical analyses classified secondary phyllosilicates related to low-moderate temperature hydrothermal fluid, very high cation exchange capacity (H+, K+, Ca2+, Mg2+), and tropical weathering. The alkaline and high alkaline basalts, presenting as parent rocks, are one of the parameters that produced good nitisal soil of Sisaket's agricultural areas.

Yakemys multiporcata n. g. n. sp., a Large Macrobaenid Turtle from the Basal Cretaceous of Thailand, with a Review of the Turtle Fauna from the Phu Kradung Formation and Its Stratigraphical Implications

Yakemys multiporcata n. g. n. sp. is described on the basis of shell elements from the upper part of the Phu Kradung Formation (basal Cretaceous), Khorat Plateau, NE Thailand and assigned to Macrobaenidae. The new taxon is unusually large for an early macrobaenid (with an estimated carapace length about 70 cm) and is characterized by a large, rounded, low shell, the presence of a midline keel and numerous additional strong ridges on the carapace, the anterolateral margin upturned to form a gutter, posterolateral peripherals mesiolaterally expanded, narrow vertebrals, the vertebral 4 triangular and narrowed posteriorly, a greatly reduced plastron with a short bridge, an oval and elongate entoplastron with reduced ventral exposure, and strip-shaped epiplastra. The discovery of a macrobaenid turtle provides further support for an Early Cretaceous age for the upper part of the Phu Kradung Formation.

Best management practices for mitigating agricultural nutrient pollution in the Mun River Basin, Thailand

The Mun River in NE Thailand is one of the significant tributaries of the Lower Mekong River. Its poor river quality has been reported and agricultural activities were claimed to be major causes. This study aims to assess the best management measures appropriately responsive to the nutrient pollution in the Mun River Basin’s agricultural ecosystems. The data used for the analysis were acquired from field measurements during the 2018 wet season via satellite retrieval and secondary data collection. Linkages between land-soil datasets and hydro-water quality datasets were assessed through a canonical correlation analysis. The results suggest possible conservation measures with crop yield improvement and fertiliser cost reduction in the western basin. For the southern basin, which exhibits high sediment loading, integrated conservation measures for soil loss reduction with in-stream flow deceleration should be chosen. In the eastern basin, woody buffer strips and check dams should be prioritised. Both nutrient and sediment pollution were experienced in the middle part of the Mun River Basin and applications of low-P manure with mineral NK are recommended. Nonetheless, other soil-water conservation measures can be optionally applied to enhance the effectiveness in the watershed management.

Middle Triassic diorites from the Loei Fold Belt, NE Thailand: Petrogenesis and tectonic implications in the context of Paleotethyan subduction

Two Early-Middle Triassic magmatic arc belts occur in the Indochina Block within Thailand, namely the Lampang Volcanic Belt and the Loei-Phetchabun Volcanic Belt, which are about 150 km apart and run parallel to each other. The Lampang Volcanic Belt has been extensively studied and suggested to be induced by eastward Paleotethyan subduction, whereas the Loei-Phetchabun Volcanic Belt has not been well constrained due to the scarcity of geochronological and geochemical data. Here we report a detailed study on zircon U–Pb dating, elemental geochemistry and Sr–Nd isotopes for the Phu Rai diorites recently identified in Loei Province, NE Thailand. The Phu Rai diorites yield Middle Triassic (ca. 239 Ma) emplacement ages. They are calc-alkaline rocks characterized by arc-like trace element patterns and depleted Sr–Nd isotopic compositions ((87Sr/86Sr)i = 0.70371–0.70392; εNd(t) = +1.65 to +2.54). These geochemical and isotopic signatures reveal that the Phu Rai diorites were most likely derived from a depleted mantle wedge metasomatized by subducted sediment-derived melts and slab-derived fluids, and modified by limited degree of fractional crystallization involving clinopyroxene, amphibole and Fe–Ti oxides combined with weak plagioclase accumulation. Based on our results and others from the literature, we suggest the existence of an Early-Middle Triassic (ca. 250–239 Ma) magmatic arc belt in NE Thailand, which is not directly linked to eastward Paleotethyan subduction, but is possibly associated with eastward subduction of the Nan back-arc basin. Specifically, the ca. 239 Ma Phu Rai diorites and ca. 245–241 Ma adakites nearby form a rock association in response to slab break-off at that time, immediately after the initial stage of the Sukhothai-Indochina collision. The occurrence of this rock association could mark not only the cessation of eastward subduction of the Nan back-arc basin but also the initiation of the Sukhothai-Indochina collision.

End-Guadalupian extinction of larger fusulinids in central Iran and implications for the global biotic crisis

The end-Guadalupian (Capitanian) biotic crisis was less intense than its end-Permian counterpart but highly selective against certain groups of tropical organisms, such as rugose corals and keriothecal-walled fusulinid foraminifera. The causes of this event remain debated, in part due to apparent disagreement among stratigraphic sections in the timing of taxonomic losses. In order to further constrain the timing of extinction and assess the broader pattern of change in benthic marine ecosystems across the Guadalupian/Lopingian boundary (GLB), here we report the stratigraphic occurrence patterns of the large, keriothecal-walled fusulinid foraminifera as well as associated skeletal grains in the Abadeh section, central Iran, which contains a relatively complete record through the GLB interval. The last keriothecal-walled fusulinid occurs within the upper Wordian at Abadeh whereas smaller fusulinids continue to occur below and above the Guadalupian/Lopingian boundary (GLB). A lithologic change from carbonates toward chert and shale within the section suggests that the local disappearance of the keriothecal fusulinids prior to the GLB reflects a facies control rather than global extinction long prior to the GLB. Re-examination of the last occurrences of keriothecal-walled fusulinids in well-studied sections of South China, Japan, NE Thailand, and Transcaucasia reveals that facies change to organic-rich sediments can explain the local disappearance of these species prior to the GLB in both Japan and NE Thailand. Apparent diachroneity of extinction in this group appears best interpreted to reflect local facies effects rather than a protracted extinction event. Global, warming-induced failure of associations between fusulinids and photosymbionts following Emeishan volcanism is the scenario most consistent with available data.

Soil salinity mapping of an urbanizing area in NE Thailand

Salinization is a growing concern of global proportions. In urban settings effective salinity management strategies must be adopted to ensure environmental sustainability in the face of rapid development. Geophysical methods, particularly electrical methods, can be used to non-invasively map the spatial distribution of subsurface groundwater salinity over wide areas at reasonable cost. In this paper, electrical resistivity tomography and vertical electrical sounding geophysical methods were used to determine the electrical resistivity structure of the subsurface beneath the rapidly developing Khon Kaen University campus in NE Thailand. The geophysical results were combined to generate a contour map of depth to saline groundwater beneath the campus. Saline groundwater was present in shallow strata in the southern part of the campus but is not indicated beneath the northern half, so that drilling for groundwater wells is recommended there. The map can be used by campus planners to inform their salinity management strategies, including the siting of groundwater wells, the design of potential soil reclamation schemes, and the location and design of buried infrastructure according to indications of soil corrosivity. The method can be applied at other urban sites located on salt-affected lands and, in general, provides a valuable supplement to costly traditional geotechnical testing.

<p><strong>A new species of <em>Dendrobium</em> (Orchidaceae: Epidendroideae: Malaxideae) described from previously perplexing specimens of the Seidenfaden collection</strong></p>

A previously unrecognized species represented by six spirit samples in the collection of the late Gunnar Seidenfaden, pioneering Danish explorer of the Thai orchid flora, is newly described. It is evident that Seidenfaden was perplexed by the material, as three different species names can be observed on the labels (often accompanied by question marks or indications such as “probably”): D. fimbriatum, D. gibsonii and D. chryseum. In our view, the new species has the strongest morphological resemblance to D. fimbriatum, but it differs in characters of the stems, leaves, lateral sepals, petals and labellum. We describe the new species as D. perplexum, the epithet referring to the previously perplexing properties of the material. So far, D. perplexum is only known from NE Thailand, but as the confirmed Thai localities are close to the Laotian border, future finds in Laos might be expected.

Phu Din Daeng, a new Early Cretaceous vertebrate locality on the Khorat Plateau, NE Thailand

In this paper, we report on a new Early Cretaceous vertebrate locality, Phu Din Daeng, in Nakhon Phanom Province, NE Thailand. The Phu Din Daeng site has yielded a diverse vertebrate assemblage, including sharks (Heteroptychodus steinmanni), bony fishes (Pycnodontiformes; Sinamiidae cf. Siamamia and ?Vidalamiinae, and Ginglymodi), adocid turtles, indeterminate neosuchian crocodiles, pterosaurs and dinosaurs (spinosaurids and indeterminate theropods). A new adocid turtle, Protoshachemys rubra n. g. n. sp. is described on the basis of shell material. Field investigations on the geology and comparisons with other vertebrate faunas place Phu Din Daeng in the Sao Khua Formation (Barremian) of the Khorat Group.

Spinosaurid teeth from the Lower Cretaceous of Ko Kut, eastern Thailand

Isolated theropod dinosaur teeth from Ko Kut (Kut Island) in eastern Thailand are referred to an indeterminate spinosaurid on the basis of their morphology and ornamentation. On the basis of other spinosaurid occurrences in Thailand and other parts of Asia, they support the attribution of the fossil-bearing beds on Ko Kut to the Lower Cretaceous rather than the Jurassic. The lack of ornithischian remains in the Ko Kut faunal assemblage suggests that it is coeval with the Sao Khua Formation (Barremian) of NE Thailand.

Kalasinemys, a new xinjiangchelyid turtle from the Late Jurassic of NE Thailand

AbstractA new xinjiangchelyid turtle, Kalasinemys prasarttongosothi n. gen. n. sp., is described on the basis of skull and shell material from the Upper Jurassic Phu Kradung Formation at Phu Noi locality, Kalasin Province, in NE Thailand. This second xinjiangchelyid turtle from Phu Noi is distinct from Phunoichelys thirakhupti by the smooth shell surface, the presence of a cervical notch, and vertebral 1 narrower than nuchal. The skull presents an arterial system characteristic of the Xinjiangchelyidae (basal Eucryptodira), and its outline is similar to that of Annemys spp. known from the Middle–Late Jurassic of China and Mongolia, but distinct from the latter mainly by the wider triturating surface, smaller foramen palatinum posterius and the shape of the prefrontal and frontal, as well as that of the basisphenoid and basioccipital. Based on the turtle assemblages, the correlation with mainland Asia further supports a Late Jurassic age for the lower part of the Phu Kradung Formation where Phu Noi site is located stratigraphically. Our study provides new insight on the evolution of the basal eucryptodiran turtles in Asia.

Societal response to monsoonal fluctuations in NE Thailand during the demise of Angkor Civilisation

This paper investigates the possible social responses to changes in the strength of the southwest monsoon in northeastern Thailand during the currency of the Angkor civilisation. These assessments are based on hydrogen and carbon isotope records of leaf waxes (δDwax and δ13Cwax) from a 2000-year-long wetland sequence of Pa Kho in northeastern Thailand, a region that formed the northern boundary of the Angkor Kingdom. Our data indicate anthropogenic flooding of the Pa Kho wetland through the control of water through dam construction from c. AD 1300 in response to the fluctuating strength of monsoon rains. δDwax, a proxy for regional hydroclimate variability, corroborates pre-existing evidence that increased summer monsoon rains, which supported the expansion of the agrarian economy, aided the rise of the Angkorian Empire whereas extreme drought contributed to its demise. Interestingly, our δDwax record shows already a gradual decreasing monsoon intensity from c. AD 1000 onwards, although Angkor’s prosperity reached its peak at c. AD 1200. We suggest that the complex hydrological system established under royal patronage at Angkor provided a resilient buffer against short-term monsoon fluctuations. The long-term decline in monsoon rains over a ~300-year period, combined with ongoing urbanisation, may have stretched the hydrological systems to their limit. We suggest that this was a major factor that contributed to the demise of Angkor in the mid-15th century.

Geochemistry of radiolarian cherts from a Late Devonian continental margin basin, Loei fold belt, Indo-China terrane

More than 42 species of well-preserved Upper Devonian radiolarians have been obtained from cherts and siliceous shales in four sections (Chom Noi, Phu Kham Phe (P), Phu Kham Phe (C) and Pha Samyod) from the NE Thailand sector of the Loei fold belt, Indochina terrane. They include Ceratoikiscum sp. cf. planistellare Foreman, Helenifore laticlavium Nazarov & Ormiston, Astroentactinia sp. cf. paronae (Hinde), Stigmosphaerostylus herculea (Foreman), S. pusilla (Hinde), S. cf. vulgaris (Won), Trilonche davidi (Hinde), T. echinata (Hinde), T. elegans Hinde, T. hindea (Hinde), T. palimbola (Foreman), T. vetusta Hinde, Polyentactinia polygonia Foreman, Spongentactinella sp. cf. windjanensis Nazarov, Archocyrtium sp.?, Palaeoscenidium sp., Triaenosphaera sp., and others. Radiolarian faunas from these sections indicate a range from lower Frasnian to Famennian. Analyses of rare earth, trace and major elements suggest that the Upper Devonian chert and siliceous successions from Loei were deposited in a continental margin environment near to a volcanic arc. These successions contain distinctive weak negative Ce anomalies with strong positive Eu anomalies which differ from Upper Devonian cherts reported from northern Thailand, the Truong Son fold belt (Laos) and from South China. Negative Ce anomalies and low to moderate Lan/Cen ratios imply proximity between the Chom Noi and Phu Kham Phe (C), which were deposited in more distal parts of the depositional basin than the Pha Samyod and Phu Kham Phe (P) samples. Most of the Pha Samyod and Phu Kham Phe (P) samples exhibit high continental-derived trace element levels including Cr, Zr, Hf, Rb, Th and in part V, which supports close proximity to terrigenous sources. Paleozoic stratigraphic sequences of the Loei fold belt and geochemical results suggest that the Upper Devonian deep marine sequences in the Loei fold belt were deposited within a rifted, continental-margin basin, possibly a back-arc basin and not in a large oceanic basin as has been previously suggested.

Large southward motion and clockwise rotation of Indochina throughout the Mesozoic: Paleomagnetic and detrital zircon U–Pb geochronological constraints

We report a combined paleomagnetic and U–Pb geochronologic study of sedimentary rocks from the Huai Hin Lat and Nam Phong formations of Mesozoic age in NE Thailand in order to provide independent constraints on the tectonic movement of the Indochina Block during convergence of the major blocks now comprising East Asia. The maximum allowable depositional age of the two formations is estimated to be 227 Ma and 215 Ma, respectively, from detrital zircon U–Pb geochronologic analysis which also indicates a sediment source transition in the Khorat Plateau Basin during the Middle–Late Jurassic. A formation mean paleomagnetic direction of Dg/Ig=21.4°/38.1° (kg=19.5, α95=9.6°) before and Ds/Is=43.0°/48.0° (ks=47.4, α95=6.1°, N=13) after tilt correction is derived from samples with different lithologies, bedding attitudes, magnetic carriers and polarities and yields a positive fold test. Hence, the magnetization is likely primary. The revised Mesozoic APWP of the Indochina Block yields paleolatitudes (for a reference site of 22°N, 102°E) of 33.4 ± 7.2°N during the Norian Late Triassic, 25.9 ± 5.9°N during the Late Triassic to Early Jurassic, 23.9 ± 8°N during the Late Jurassic to Early Cretaceous, 27.5 ± 3.2°N during the Early Cretaceous and 24.5 ± 4.9°N by the Late Cretaceous; corresponding declinations are 45.2 ± 8.6°, 38.0 ± 6.6°, 36.3 ± 8.8°, 29.6 ± 3.6° and 24.9 ± 5.4° respectively. These data indicate a significantly southward displacement accompanied by clockwise rotation during the Mesozoic. A reconstruction of the Indochina Block within the now well-studied merging process of South China and North China indicates that the Indochina Block was located at a higher latitude than the South China Block during the Norian stage of Late Triassic times whilst no significant relative poleward displacement apparently occurred during the Early Jurassic to Early Cretaceous interval. Our study supports a post-Cretaceous tectonic extrusion model with a southeastward displacement of Indochina with respect to the South China Block estimated to be 1000 ± 850 km since the Late Cretaceous.