Dipterocarpus Obtusifolius Research Articles

Diversity and ecological role of Dipterocarpus obtusifolius Teijsm. ex Miq. in Nui Cau - Dau Tieng protection forest, Binh Duong province

Studying the diversity and ecological role of dominant species provides an important foundation for understanding the influence of dominant species on the diversity and biomass production capacity of plant communities. This study was conducted at the Nui Cau - Dau Tieng Protection Forest Management Board, Binh Duong province, to understand the diversity and ecological role of Dipterocarpus obtusifolius Teijsm. ex Mig. in the ecosystem forests. A total of 19 plots, each 0.1 ha in size (50 m x 20 m), were used for data collection. Trees with a diameter at breast height (dbh) ≥ 6 cm were recorded, including species name, number of individuals, dbh, and overall height. The study employed importance value index analysis (IVI%) and aboveground biomass (AGB) to assess the ecological role of dominant species. Findings revealed that: (1) Communities with dominant species had low species richness and fluctuating diversity levels, (2) The ecological role of dominant species varied across forest states, decreasing from very poor > poor > medium forests, and (3) Increasing IVI% and AGB% of dominant species influenced woody species structure and biomass output in the plant community. This study offers valuable insights to enhance forest management and quality in the area.

Edge tree functional traits and their association with edaphic factors in seasonally dry forests in northern Thailand

The relationships between plant traits and soil properties in forest edges can provide insights into tree species recovery in edge habitats. In this study, we investigated the relationships between plant functional traits and soil conditions related to tree species recovery at the edges of two seasonally dry forests, a mixed deciduous forest (MDF) and a deciduous dipterocarp forest (DDF) in northern Thailand. We analyzed differences in functional trait diversity and community-level trait values between forests and performed RLQ analysis to assess the associations among species abundance, plant traits, and soil variables. We found that the MDF site had greater functional diversity and was dominated by plants with high specific leaf area (SLA) and leaf dry-matter content (LDMC) at the community level, whereas the DDF site had lower diversity and was dominated by plants with high wood density (WD) and leaf thickness (LT). The RLQ results indicated that at the MDF site, tree species with greater SLA (e.g., Pterocarpus macrocarpus, Dalbergia cultrata, and Phanera bracteata) were associated with soil clay content and nutrient status (i.e., nitrogen and calcium). Species with greater LDMC and leaf size (e.g., Xylia xylocarpa, Schleichera oleosa, and Chukrasia tabularis) were associated with soil organic matter content. At the DDF site, species with greater WD and LT (e.g., Dipterocarpus obtusifolius, Shorea siamensis, and Buchanania lanzan) were associated with soil sand content and bulk density. These patterns reflect the interplay between soil conditions and plant traits in the edge habitats of seasonally dry forests. Our results indicate that the edge effects on plant communities within seasonally dry forests depend on soil conditions and species-specific plant traits.

Tree diversity and species composition of tropical dry forests in Vietnam's Central Highlands Region

Abstract Tree species inventories, particularly of poorly known dry forests, are necessary to protect and restore them in degraded landscapes. The present research has been conducted to compare taxonomic diversity and community composition in four dry forests (DF) categories with different standing volume levels: very low (DFV), low (DFP), medium (DFM) and high (DFR). This quantitative assessment of taxonomic diversity, forest structure and species composition were obtained from 103 sample plots (0.1 ha each). The regeneration potential of trees was assessed in 515 subplots (4 m × 4 m) located within the 103 plots. A total of 1,072 trees representing 87 species belonging to 37 families were recorded in 10.3 ha of total sampled area. The ranges of diversity indices observed in the four forest types were: Margalef's (5.44–8.43), Shannon-Wiener (1.80–2.29), Simpson diversity (0.76–0.87) and evenness (0.32–0.35). The regeneration potential of rare and threatened species Dalbergia oliveri, Hopea recopei, Dalbergia bariensis, Sindora siamensis, Parashorea stellata was observed to be poor. Conversely, Cratoxylon formosum, Shorea obtusa, Dipterocarpus tuberculatus, Dipterocarpus obtusifolius, Terminalia alata, Shorea siamensis and Xylia xylocarpa were the most dominant species at the seedling and sapling stage, showing a strong potential for regeneration. Overall, this study provides useful information on tree species diversity and composition for tropical dry forests which can be used as baseline data to develop incoming plans for forest management and conservation in Vietnam's Central Highlands Region.

Restoration of Water Storage Potential in a Degraded Dry Dipterocarp Forest with Enrichment Planting of Three Needle Pine (Pinus kesiya Royle ex Gordon), Northern Thailand

The research assessed water storage in a dry dipterocarp forest (DDF) with enriched 34-year-old pine planting and the role of pine. Plant surveys were carried out using 10, 40×40 m2 plots, and data were obtained by measuring tree stem girths and heights. Plant features, biomass, and stored water amounts were measured. Fresh plant samples of abundant species were taken one time per month from January to December 2018. Three soil pits were made in three plots, and soil samples along 100 cm depth were taken on the same days of collecting plant samples for studying fied capacity, water content and water amount. The DDF was divided into three stands based on the most dominant tree species; Shorea obtusa, Dipterocarpus tuberculatus, and Dipterocarpus obtusifolius. The forest was composed of 86 species with biomass at 101.62 Mg/ha and contained an average water amount of 88.01 m3/ha. The water amount in biomass varied with sampling times from 58.74 to 111.83 m3/ha. The average MWHC of 100 cm soil was estimated to be 5,113.74 m3/ha. The water amount in soil also varied with sampling times from 3,651.50 to 4,481.06 m3/ha. As a result, the total water amount in plant biomass and soil (ecosystem) of the DDF varied in a range from 3,735.0 to 4,558.67 m3/ha. The pine contributed to 30.87 m3/ha (35.07% of the total) and could increase by 64.92% the water storage potential of the forest, and thus these results support the concept of pine enrichment planting in the poor DDF.

Impact of Severe Drought during the Strong 2015/2016 El Nino on the Phenology and Survival of Secondary Dry Dipterocarp Species in Western Thailand

Secondary forest areas are increasing worldwide and understanding how these forests interact with climate change including frequent and extreme events becomes increasingly important. This study aims to investigate the effects of the strong 2015/2016 El Niño-induced drought on species-specific leaf phenology, dieback and tree mortality in a secondary dry dipterocarp forest (DDF) in western Thailand. During the 2015/2016 El Niño event, rainfall and soil water content were lower than 25 mm and 5% during 5–6 consecutive months. The dry season was 3–4 months longer during the El Niño than during non-El Niño events. We found that this prolonged drought induced the earlier shedding and a delay in leaf emergence of the DDF. The deciduousness period was also longer during the El Niño event (5 months instead of 2–3 months during non-El Niño event). We found that the DDF species showed different phenological responses and sensitivities to the El Niño-induced drought. The leaf phenology of stem succulent species Lannea coromandelica (Houtt.) Merr. and a complete deciduous species with low wood density. Sindora siamensis Teijsm. ex Miq. was only slightly affected by the El Niño-induced drought. Conversely, a semi-deciduous species such as Dipterocarpus obtusifolius Teijsm. ex Miq. showed a higher degree of deciduousness during the El Niño compared to non-El Niño events. Our results also highlight that dieback and mortality during El Niño were increased by 45 and 50%, respectively, compared to non-El Niño events, pointing at the importance of such events to shape DDF ecosystems.

The existence of a fire‐mediated tree‐recruitment bottleneck in an Asian savanna

AbstractAimA considerable proportion of the global savanna biome has been mis‐classified as forest, especially in Asia. However, the structure and responses of dominant tree species to fire can help to clarify this ambiguity. Here, we examine demographic structure and fire responses of four dominant tree species in a deciduous dipterocarp forest (DDF) of the continental Southeast Asia. We examine whether fire creates a tree‐recruitment bottleneck in the DDF, as in savannas on other continents.LocationYokDon National Park, Vietnam.TaxonDipterocarpus tuberculatus Roxb.; Dipterocarpus obtusifolius Teysm. ex Miq.; Shorea obtusa Wall. ex Blume; Shorea siamensis (Kurz) Miq.MethodsWe measured the size of all 8,288 individuals of the four dominant dipterocarp species in 12 pair study sites. We then applied fire treatments (burnt or unburnt) to the plots and monitored the survival and growth of juveniles five times over the subsequent growing season.ResultsAll four species showed clear indications of a recruitment bottleneck at the sapling stage. Almost all juveniles in the burnt plots suffered aboveground mortality, but 64% resprouted by the end of the following growing season. Compared to large juveniles, small juveniles had a significantly higher probability of aboveground mortality and a more limited ability to resprout. Within 3 months of fire, 43%–93% of individuals had resprouted, and they had recovered 67%–95% of their pre‐fire basal diameter and 43%–94% of their pre‐fire height. At the end of the post‐fire growing season, burnt juveniles experienced virtually no net increase in size; however, juveniles in unburnt plots attained up to 150% of their pre‐fire size.Main conclusionsThe four dominant tree species of the DDF show remarkable similarities in the demographic structures and fire‐responses with savanna tree species on other continents. Our results are consistent with the notion that the DDF is functionally similar to savannas on other continents. Fire appears to act as potent environmental filter of tree species composition in the DDF.

Dipterocarpusobtusifolius attenuates the effects of lipopolysaccharide‑induced inflammatory response in RAW264.7 macrophages.

Dipterocarpusobtusifolius has been traditionally used as a herbal medicine and is considered to have anticancer properties. The biological activity of D. obtusifolius in inflammation and the underlying mechanisms of its activity remain to be elucidated. The present study investigated the effects of D. obtusifolius methanolic extract (DOME) on lipopolysaccharide (LPS)‑stimulated inflammation in RAW264.7 cells. The effects of DOME on the production of nitric oxide, prostaglandin E2 and pro‑inflammatory cytokines were assessed by ELISA, western blot analysis and reverse transcription‑quantitative polymerase chain reaction. It was demonstrated that expression of inducible nitric oxide synthase, cyclooxygenase‑2, interleukin‑1β and tumor necrosis factor‑α was suppressed by DOME in LPS‑stimulated cells. Furthermore, treatment with DOME suppressed phosphorylation of mitogen activated protein kinase (MAPK) molecules, including extracellular signal‑regulated kinase, c‑Jun N‑terminal kinase and p38 MAPK. Translocation of the nuclear factor‑κB p65 subunit into the nucleus was additionally inhibited by DOME. Phosphorylation of MAPK promoter activity was inhibited by treatment with DOME, PD98059, SB202190 and SP600125. These results demonstrated that DOME inhibits LPS‑induced inflammatory responses. Therefore, DOME may be a potential therapeutic approach for the treatment of inflammatory diseases.

Diversity and Traditional Knowledge of Textile Dyeing Plants in Northeastern Thailand

The objective of this study was to document the traditional knowledge of plants used for textile dyeing by the Tai-Lao ethnic group in Roi Et province in northeastern Thailand. Traditional knowledge of plants used for textile dyeing is disappearing because of modernization including new lifestyles, urbanization, and the introduction of synthetic colors. Textile dyeing with local plants, however, is experiencing a revival connected to ecotourism and global interest in natural products. To exploit that potential, it is important to preserve the local knowledge related to textile dyeing. We interviewed 60 Tai-Lao informants in 15 villages and 9 districts about their dyeing traditions and the species used through individual semi-structured and focus groups interviews. A total of 56 species in 50 genera and 31 families were used for dyeing cotton and silks; most species belonged to Fabaceae (11 spp., 19%) and Anacardiaceae (5 spp., 9%). Trees (36 spp., 65%) were the best represented life form among the dye plants, followed by shrubs and herbs (8 spp., 16% each), and climbers (4 spp., 7%). Bark was the plant part most commonly used for dyeing (25 spp., 42%) followed by leaves (12 spp., 20%), and fruits (9 spp., 15%). Home gardens were the most common habitat of dye plant (30 spp., 53%) followed by community forests (16 spp., 28%). Indigofera tinctoria L. and Pterocarpus indicus Willd. were the most important dye plant species of the Tai-Lao ethnic group as demonstrated by their high use value index (UV = 0.60). Blue/indigo-blue was the color most informants had common knowledge about with an informant consensus factor (ICF) of 0.92 followed by black with ICF = 0.84. Ten different colors were obtained from the 56 plant species. Brown/pale-brown/golden-brown was the color obtained from most dye plant species (14 spp., 25%) followed by green/pale-green/dark-green (13 spp., 23%). Nine different kinds of mordants were used in the dyeing, including alum, chrome (potassium dichromate; K2Cr2O7), copper sulfate (CuSO4), iron oxide (Fe2O3), tamarind juice (tartaric acid), salt (NaCl), lime (calcium oxide; CaO), ash (potassium hydroxide; KOH), and mud. Among the 56 species used for textile dyeing, three are on the IUCN Red List of Threatened Species, including: Dipterocarpus alatus Roxb. & G.Don, Dipterocarpus obtusifolius Teijsm. ex Miq., and Pterocarpus indicus Willd. Documenting these and other species used for textile dyeing will provide additional arguments for their conservation. It will also help to secure the reappearing tradition of textile dyeing with local plants, and hence support the cultural integrity of the Tai-Lao communities, and serve as an example for other communities in Thailand and elsewhere for preserving their traditional knowledge.

Tropical tree water use under seasonal waterlogging and drought in central Cambodia

Summary In central Cambodia, rapid growing non-endemic species are planted for future timber production. However, less is understood about the impact of the introduction of non-endemic species on the transpiration characteristics of the forest, which has been composed of native species that adapted to the highly seasonal environments. Sap flux of two native and one non-endemic tree species in central Cambodia was measured to reveal its seasonal trends and variability in the Monsoon Asia region. Measurements were carried out in a 10- to 15-year-old forest in the dry and rainy seasons that were defined by differing rainfall patterns. The seasonal trend in depth to water table differed from that of rainfall; groundwater table depth reached zero late in the rainy season and increased gradually after the onset of the dry season. The ratio of sap flux to an equilibrium evaporation condition of the native species, Popel ( Shorea roxburghii ), showed a sharp decline at the end of the dry season, whereas that of a non-endemic species, eucalyptus ( Eucalyptus camaldulensis ), decreased in the mid rainy season while Tbeng ( Dipterocarpus obtusifolius ) did not show a clear trend. The ratio of sap flux to an equilibrium evaporation was negatively correlated with the depth to water table in Popel, but was positively correlated in eucalyptus, possibly because of the negative effects of flooding. In addition to the large seasonal variation, intra-species variation in sap flux was also large and was a major controlling factor for tree-level water uptake at this young forest site in both dry and rainy seasons. In conclusion, the transpiration characteristics of this forest were species-specific and were controlled more by the fluctuating depths to groundwater rather than the onset of the rainy/dry seasons defined by rainfall events.

ChemInform Abstract: Cytotoxic Terpenes from the Stems of Dipterocarpus obtusifolius Collected in Cambodia.

AbstractFive new triterpenes are isolated from the stems of dipterocarpus obtusifolius along with 13 known compounds.

Potential Energy Resources from Dipterocarp Leaf Litter and the Potential in Air Pollution Reduction in Mae Hong Son Province, Thailand

Dense clouds of smoke hang in the air over the Mae Hong Son province caused by intense forest fires is a significant source of air pollution which is the most hazardous to environment and public health, particularly during November to April each year. This study is aimed to exploit the energy potential of leaf litter from various plants in dipterocarp forest of Mae Hong Son Province. Five tree species with high IVI show the energy potential as follows: Shorea obtusa 4,950 Kcal/Kg, Dipterocarpus tuberculatus 4,679Kcal/Kg, Shorea siamensis 4690 Kcal/Kg, Dipterocarpus obtusifolius 4674 Kcal/Kg and Quercus kerrii 5137 Kcal/Kg. During the fire season there is an average of 449.58 tons of leaf litter per Rai (1600 m 2 ).We can collect these leaves and turn them into fuel which means reducing the percentage of air pollution and the amount of firewood the inhabitants gather for their use up to 86,400 tons per year.

Fuelwood consumption patterns in Chumriey Mountain, Kampong Chhnang Province, Cambodia

The study was carried out to explore fuelwood consumption rate for different activities, such as cooking, boiling water, preparing animal feed and burning to protect cattle against insects; species preference; and to examine the characteristics of cook stoves. Approximately 96% of sampled households depend on fuelwood as a primary source for cooking, boiling water, preparing animal feed and protecting cattle against insects. Average fuelwood consumption for cooking and boiling water in very large families is significantly higher than that with very small families. Overall average fuelwood consumption for cooking and boiling water per family per day is 5.21 ± 0.11 kg and 2.82 ± 0.11 kg. Households with a high number of cattle or pigs consume a higher amount of fuelwood for producing smoke to protect cattle against insects or preparing pig feed. The average fuelwood consumption rate is approximately 5.60 ± 0.11 kg day−1 family−1 for repelling insects to protect animals and 3.90 ± 0.19 kg day−1 family−1 for preparing pig feed. The most preferred species is Shorea obtusa followed by Dipterocarpus obtusifolius, Xylia xylocarpa, Cratoxylon prunifolium, and Dipterocarpus tuberculatus. Two models of improved cooking stoves (the New Lao Stove and the Korng Rey Stove) are the most frequently used stove type in the study area.

Cytotoxic Terpenes from the Stems of <i>Dipterocarpus obtusifolius</i> Collected in Cambodia

From the stems of Dipterocarpus obtusifolius, five new triterpenes, 3-oxo-20-hydroxy-30α-methyl,17(29)α-epoxy-28-norlupane (1), 3-oxo-20-hydroxy-30β-methyl-17(29)α-epoxy-28-norlupane (2), 3,20-dioxo-28,29-norlupan-17α-ol (3), 27-demethyl-20(S)-dammar-23-ene-20-ol-3,25-dione (4), and 3-epi-cecropic acid (5) together with 13 known compounds including diterpene, sesquiterpenes and triterpenes were isolated and characterized. All isolates were tested for their cytotoxicities against a small panel of human cancer cell lines. Of the tested compounds, compounds 4-11 were found to be cytotoxic against one or more human cancer cell lines.

Dipterocarpus obtusifolius exhibits enhanced photosynthetic capacity at high temperatures

Seedlings planted on degraded lands experience high leaf temperature in daytime because of the lack of vegetation shading. The effect of high temperature on the photosynthetic capacity was investigated in Dipterocarpus obtusifolius Teijsm. ex Miq. and D. chartaceus Sym. seedlings planted on degraded sandy soils in southern Thailand. Neither species showed decrease in photosynthetic capacity at leaf temperature over 38 °C as compared to that at 28 °C. D. obtusifolius showed higher photosynthetic capacity at high temperatures. Enhanced photosynthetic capacity at high temperatures would be a key for high photosynthetic performance of D. obtusifolius planted on degraded sandy soils.

Photosynthetic characteristics of dipterocarp species planted on degraded sandy soils in southern Thailand

To elucidate whether dipterocarp species, dominant late-successional species of tropical forests in Southeast Asia, actually have a disadvantage when planted on open site in terms of their photosynthetic characteristics, we investigated photosynthesis in dipterocarp seedlings planted in the open on degraded sandy soils in southern Thailand. These species were compared with seedlings of Acacia mangium Willd., a fast-growing tropical leguminous tree, which is often planted on degraded open site in Southeast Asia. The dipterocarp seedlings had an irradiance-saturated net photosynthetic rate (PN), stomatal conductance (gs), carboxylation efficiency, and photosynthetic capacity comparable to or superior to those of A. mangium. In particular, seedlings of Dipterocarpus obtusifolius Teijsm. ex Miq. showed an irradian-ce-saturated PN of 21 µmol m-2 s-1, a value higher than any previously reported for a dipterocarp species, accompanied by high gs (0.7 mol m-2 s-1) and high photosynthetic capacity. Thus dipterocarp species do not necessarily have a disadvantage in terms of their photosynthetic characteristics on open sites with degraded sandy soils.

Nitrogen form preference of six dipterocarp species

We investigated the nitrogen form preference of six dipterocarp species: Anisoptera costata Korth., Dipterocarpus obtusifolius Teijsm. ex Miq., Hopea odorata Roxb., Neobalanocarpus heimii (King) P. Ashton, Shorea faguetiana Heim, and Shorea roxburghii G. Don. Seedlings were supplied with nitrogen as nitrate, ammonium, or both in sand culture in a controlled environment. Except for N. heimii, all species showed greater shoot growth when supplied with ammonium than with nitrate. Higher root mass ratios were observed in all species with nitrate, which would be an adaptive response to limited nitrogen uptake. The five species, which preferred ammonium, showed a higher light-saturated photosynthetic rate with ammonium supply. The lower light-saturated photosynthetic rate with nitrate supply was a result of lower photosynthetic capacity, as indicated by a lower CO 2-saturated photosynthetic rate. The lower leaf nitrogen content in seedlings supplied with nitrate would be the cause of the lower photosynthetic performance. Nitrate reductase activity in leaf and root of D. obtusifolius, N. heimii, and S. roxburghii showed generally low inducibility with nitrate.

Alien Abduction: Disruption of Native Plant‐Pollinator Interactions by Invasive Species

ABSTRACTThe indirect impacts of Shorea siamensis‐logging on the reproductive ecology of Dipterocarpus obtusifolius, a self‐incompatible butterfly‐, moth‐, and bird‐pollinated tree, were studied in tropical dry forest in Thailand. Pollinator activity at D. obtusifolius trees and subsequent seed production were recorded in three forest areas subject to differing intensities of S. siamensis extraction. The pollinator and plant understory communities in these areas were also noted. Forest areas subject to high S. siamensis extraction intensities had very high understory flowering plant cover, dominated by the exotic invader Chromolaena odorata. Activity of butterfly pollinators at D. obtusifolius trees decreased in these disturbed areas, although their abundance remained comparable to other forest areas subject to only moderate or no extraction. For sphingid moth pollinators, there was no difference across differentially disturbed forest areas in either abundance or in the proportion bearing pollen. Pollinator activity by birds increased at highly disturbed locations but was not sufficient to offset a decline in overall pollinator activity at D. obtusifolius canopies in areas of heavy 5. siamensis extraction. Thus, extraction of S. siamensis indirectly affected the pollination of D. obtusifolius, primarily by causing changes in the foraging behavior of butterfly pollinators rather than their abundance. A shift in the relative abundance of floral nectar resources from the canopy to the understory, a consequence of 5. siamensis extraction and invasion by C. odorata, led to a parallel shift in foraging location of the principal diurnal pollinators, the butterflies, toward the understory. Despite reduced pollination at disturbed sites, behavioral changes did not translate into a D. obtusifolius seed set effect, possibly because pollination by birds (or moths) at the disturbed site compensated for reduced butterfly pollination.

Alien Abduction: Disruption of Native Plant-Pollinator Interactions by Invasive Species1

ABSTRACT The indirect impacts of Shorea siamensis-logging on the reproductive ecology of Dipterocarpus obtusifolius, a self- incompatible butterfly-, moth-, and bird-pollinated tree, were studied in tropical dry forest in Thailand. Pollinator activity at D. obtusifolius trees and subsequent seed production were recorded in three forest areas subject to differing intensities of S. siamensis extraction. The pollinator and plant understory communities in these areas were also noted. Forest areas subject to high S. siamensis extraction intensities had very high understory flowering plant cover, dominated by the exotic invader Chromolaena odorata. Activity of butterfly pollinators at D. obtusifolius trees decreased in these disturbed areas, although their abundance remained comparable to other forest areas subject to only moderate or no extraction. For sphingid moth pollinators, there was no difference across differentially disturbed forest areas in either abundance or in the proportion bearing pollen. Pollina...

The pollination and breeding system of Dipterocarpus obtusifolius (Dipterocarpaceae) in dry deciduous forests of Thailand

The pollination biology of Dipterocarpus obtusifolius (Teijsm.), an obligately insect-pollinated dry deciduous dipterocarp tree, is described. For the first time, the pollinators of a Dipterocarpus species are identified, and they are found to be large Lepidoptera, a new pollination syndrome for this tree family. D. obtusifolius produces relatively few large, pink, pendulous flowers that emit a strong fragrance upon opening. Flowers open at dusk and remain open for 24–36h. Nectar secretion occurs at flower opening and continues through the next day. Pollen is maximally available at night but much pollen remains available to daytime visitors. The stigma is spatially separated from the anthers but pollen presentation and stigma receptivity occur simultaneously. In artificial pollination experiments there was intense selection pressure, through abscission of young fruit, in favour of outcrossing. Pollination did not occur in the absence of insect vectors. Large moths (Sphingidae and Noctuidae) are the primary pollination vectors at night and account for 60% of pollen transfer. Butterflies (primarily Pieridae and Papilionidae) pollinate flowers during the day. It is likely that birds pollinate a small proportion of flowers. The pollination syndrome and breeding system of this species is discussed in relation to its biogeography.

Effects of trees on paddy bund on soil fertility and rice growth in Northeast Thailand

A study was conducted in Northeast Thailand on six rice paddy fields on a farm with similar soil (Aquic Quartzipsamments) and with a single tree on the paddy bund. There were 4 tree species: Parinarium anamense, Dipterocarpus obtusifolius, D. intricatus, and Samanea saman. Samples of soil (0–10 cm depth) and rice were collected at 3 positions (1, 5–7, and 9–11 m) away from the tree base in 3 replicated tree-soil trasects in each paddy field. Significantly higher pH, organic matter, and nutrients (N, P, K, Ca, and Mg) were found in paddy fields with S. saman (a legume tree) but grain yield and biomass of rice were significantly lower. Higher soil fertility was found in the positions closer to tree base while grain yields, biomass, and number of tillers were lower, and rice was taller and had more unfilled grain. Shading was deduced to be the key factor responsible for the depressed rice yields and growth at positions closer to tree base especially in the highly shading S. saman.