Hubbry Logo
Dipterocarpus retususDipterocarpus retususMain
Open search
Dipterocarpus retusus
Community hub
Dipterocarpus retusus
logo
8 pages, 0 posts
0 subscribers
Be the first to start a discussion here.
Be the first to start a discussion here.
Dipterocarpus retusus
Dipterocarpus retusus
Dipterocarpus retusus
View on Wikipedia
from Wikipedia

Dipterocarpus retusus
from Koehler's Medicinal-Plants (1887)
Scientific classification Edit this classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Malvales
Family: Dipterocarpaceae
Genus: Dipterocarpus
Species:
D. retusus
Binomial name
Dipterocarpus retusus
Synonyms[2]
  • Dipterocarpus macrocarpus Vesque
  • Dipterocarpus mannii King ex Kanjal, P.C.Kanjal & D.Das
  • Dipterocarpus pubescens Koord. & Valeton
  • Dipterocarpus spanoghei Blume
  • Dipterocarpus tonkinensis A.Chev.
  • Dipterocarpus trinervis Blume
Sapling at Hoollongapar Gibbon Sanctuary, Assam

Dipterocarpus retusus, commonly known as hollong,[3] is a large tree and perhaps the best known species in the genus Dipterocarpus. It is native to China, Vietnam, Philippines, Laos, Cambodia, Malaysia, Indonesia, Myanmar, and India.[1][4] The tree, some 20–30 metres (70–100 ft) tall, is found in Cambodia in dense forests of the plains, common on hillsides and along rivers and in forests between 800 m (2,600 ft) and 1,500 m (5,000 ft) altitude.[4]

In Vietnam

Hollong is the state tree of Assam and Arunachal Pradesh, India.[5] In India, the timber is used for plywood and making various containers. In China, the timber is used in construction.[1] Hollong is a sacred tree for Moran community of Assam.[citation needed]

Uses

[edit]

It is farmed for its timber and resin. In Cambodia, the resin is collected by people in the mountainous regions, in order to make torches and candles, while the wood is used in construction to make columns and boards.[4]

References

[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Dipterocarpus retusus

View on Grokipedia
from Grokipedia
Dipterocarpus retusus is a large tree in the family , commonly known as hollong, native to tropical , where it can reach heights of 10–50 meters with a straight, cylindrical bole up to 15–20 meters long and 100–150 cm in diameter. The species features ovate to elliptic or oblong leaves measuring 14–40 cm long, which are glabrous above and pubescent beneath, solitary white flowers, and distinctive ovoid fruits with long, wing-like calyx lobes 10–25 cm in length. This tree inhabits moist and montane forests, typically at elevations of 100–1,300 meters, thriving in deep, fertile, well-drained soils with a of 5–5.5 and annual rainfall between 1,550–4,550 mm. It prefers temperatures of 22–30°C and tolerates partial shade when young, emerging as a dominant canopy species in mature rainforests. Ecologically, D. retusus supports in tropical lowland and montane ecosystems, contributes to , and regulates water and soil cycles as a key component of dipterocarp-dominated forests. The native range extends from in through Indo-China (, , , , ) to southern (western and southeastern ), , (including the ). It is harvested from the wild for its valuable timber, which is used in , furniture, , and as fuelwood, while its serves as a , , torch fuel, and agent; the is also planted ornamentally and as a in . Dipterocarpus retusus is classified as Endangered on the (as assessed in 2017) due to severe threats from , for timber and , , , and , with global population declines estimated at over 50% in the past three generations (approximately 300 years). In , it holds cultural significance locally and is protected in wildlife sanctuaries like Dehing Patkai and Hollongpar Gibbon, though ongoing conservation efforts emphasize community-based protection and reforestation to mitigate its decline.

Taxonomy

Classification

Dipterocarpus retusus is classified in the kingdom Plantae, phylum Tracheophyta, class Magnoliopsida, order Malvales, family Dipterocarpaceae, genus Dipterocarpus, and species D. retusus, with the authority attributed to Carl Ludwig Blume in 1823. This species is one of approximately 70 in the genus Dipterocarpus, which is notable within the Dipterocarpaceae family for its dominant role in the structure and ecology of Southeast Asian tropical forests. Dipterocarpus retusus was first formally described by Blume in 1823, in his work Catalogus van eenige der merkwaardigste in en om de stad Buitenzorg groeiende gewassen.

Etymology and Synonyms

The genus name Dipterocarpus is derived from the Greek words di- (two), pteron (wing), and karpos (fruit), alluding to the characteristic two elongated wings on the calyx of the fruit. The specific epithet retusus originates from the Latin adjective meaning "blunted" or "rounded at the apex," referring to the emarginate or retuse tip of the leaves. Accepted synonyms of Dipterocarpus retusus include D. tonkinensis A.Chev., which was described from specimens in but later synonymized due to overlapping morphological traits with the typical form; D. austroyunnanicus Y.K.Yang & J.K.Wu and D. luchunensis Y.K.Yang & J.K.Wu, both from Yunnan Province in , reduced to synonymy based on shared vegetative and reproductive features; and D. macrocarpus Vesque (in part), where certain variants from Indo-China were merged owing to insufficient diagnostic differences. Additional heterotypic synonyms encompass D. trinervis Blume and D. mannii King ex Kanjilal, recognized through taxonomic revisions that emphasized continuity in fruit and leaf characteristics across populations. The species exhibits notable morphological variation, particularly at the extremes of its range from southern to , such as differences in leaf size (14–40 cm long) and fruit wing proportions, which historically fueled synonym debates but have been resolved by modern integrative incorporating genetic and ecological data.

Description

Morphology

Dipterocarpus retusus is an to that attains heights of 40-48 m, featuring a straight cylindrical bole up to 20 m branch-free with a of 100-150 cm. The bark is gray to brown, shallowly flaky, and not deeply fissured except possibly at the base. Leaves are alternate, ovate to elliptic or oblong, measuring 14–30 long by 8–18 wide, leathery, glabrous above, and bearing rusty pubescence beneath when young, with the apex acute. Flowers are hermaphroditic, cream-colored with a tinge, sweetly scented, with narrowly elliptic petals 5–6 long bearing dense squamate hairs, and (25–)30 stamens; borne in axillary racemes 8–10 long with 2–5 flowers each, consisting of 5 sepals—two of which elongate into wings after —and 5 petals. Fruits are ovoid nuts 1-1.5 cm long, crowned by a persistent calyx bearing two wings 10–25 cm long that facilitate wind dispersal; this winged structure is emblematic of the genus , reflecting its etymological roots.

Reproduction

Dipterocarpus retusus exhibits a flowering typical of many dipterocarp species, with blooms occurring irregularly, typically at the end of the across much of its range in , though flowering can be synchronized during mast years, where large-scale community-level flowering events enhance by synchronizing and seed production. Such mast flowering is a characteristic strategy in dipterocarp forests, often triggered by climatic cues like El Niño events, leading to supra-annual pulses of reproduction. Pollination in D. retusus is predominantly entomophilous, facilitated by such as , bees, and beetles, which are common pollinators in dipterocarp communities. The flowers are protandrous, with male phases preceding female phases to encourage and reduce , a mechanism observed in related dipterocarp species and likely applicable here. While wind may play a minor supplementary role, vectors are essential for effective pollen transfer in the dense forest . Fruiting follows flowering by several months, with regional variations. The fruits are nut-like with two prominent calyx wings measuring 10-25 cm in length, which enable anemochorous dispersal by during fall, allowing seeds to travel distances of 50-150 m from parent trees. This wind-assisted mechanism is crucial for colonizing canopy gaps in lowland forests. Seeds of D. retusus are large and recalcitrant, with viability typically ranging from 50-80% under optimal fresh collection conditions, though rates can drop to 20-30% or lower due to sensitivity and requiring immediate in moist, shaded for . Natural regeneration is slow, as seedlings exhibit moderate but struggle in deep shade without light exposure, persisting for years in before responding to canopy disturbances. Propagation is mainly sexual through seeds, which must be collected promptly after fruit drop to maintain viability; vegetative methods, such as stem cuttings or from leaf tissues, are possible but rare in natural settings and used primarily in cultivation for conservation.

Distribution and Habitat

Geographic Range

_Dipterocarpus retusus is native to a broad region spanning the and , with its range extending from through the to the Indonesian archipelago. In , it occurs primarily in and within the East Himalaya region. The species is also found in , southern (including , South-Central China, and ), , , , , and . Further south and east, populations are recorded in Indonesia, encompassing Sumatra, , and the , as well as in (Peninsular Malaya). Disjunct populations may exist in the . Historically, the species was more widespread across the hotspot, which covers much of its core native distribution from the to the River basin, but current populations are fragmented due to habitat loss. Core remaining populations persist in the eastern Himalayan foothills and the Mekong region, including montane forests in and . In , the range reaches its southern limit in the , reflecting a disjunct pattern within . The has been introduced and planted in areas beyond its native range for and ornamental purposes. In , it is cultivated as a timber crop in plantations. Small-scale plantings occur in parts of , including , and ornamental uses are noted in northern Indian urban settings.

Environmental Preferences

_Dipterocarpus retusus primarily inhabits lowland to montane tropical moist forests, occasionally extending into semi-deciduous formations, and is commonly found on hillsides, riverbanks, and within mixed dipterocarp stands across . These habitats include seasonal dipterocarp forests in regions such as and , where the species contributes to the canopy layer in both primary and settings. The species thrives in a tropical wet climate characterized by annual rainfall ranging from 1,550 to 4,550 , with optimal conditions between 2,500 and 3,500 , and mean temperatures of 22–30°C, tolerating extremes from 5–38°C. It accommodates seasonal dry periods in monsoon-influenced areas but is intolerant of , aligning with its distribution in everwet and seasonal tropical environments where mean annual rainfall exceeds 1,000 and humidity remains high. Dipterocarpus retusus prefers well-drained loamy or sandy soils that are deep and fertile, with a of 5–5.5 and tolerance up to 4.5–6, though it can adapt to a range of textures from deeply weathered and ultisols to temporarily flooded or dry sandy areas. It occurs at elevations from 100 to 1,500 m, showing a preference for altitudes below 1,000 m in , while extending up to 2,000 m in southern . In these environments, D. retusus co-occurs with other dipterocarps such as and Hopea species, often dominating the upper canopy in mixed stands that enhance forest structure and . This association underscores its role in maintaining the ecological integrity of tropical moist forests, where it regenerates under partial shade before requiring full light for maturation.

Ecology

Community Role

Dipterocarpus retusus occupies the emergent canopy stratum in Southeast Asian tropical rainforests, where it reaches heights of up to 40 meters, providing essential shade that moderates microclimates and supports plant diversity. As a dominant species in dipterocarp-dominated s, where dipterocarps often comprise 50-60% of emergent individuals, it contributes substantially to overall and enhances structural complexity that fosters for epiphytes and arboreal . This positioning enables D. retusus to play a pivotal role in maintaining canopy integrity, which in turn influences light penetration and humidity levels critical for lower layers. The species forms ectomycorrhizal symbioses with fungi, particularly from families such as (e.g., _ spp.) and , which colonize its to facilitate enhanced uptake of nutrients like and in nutrient-poor tropical soils. These associations improve seedling establishment and overall vigor by extending the root system's , allowing D. retusus to thrive in oligotrophic environments typical of its . Such mutualistic relationships underscore its to challenging edaphic conditions, promoting resilience in mixed dipterocarp communities. D. retusus interacts extensively with , serving as a source and provider that bolsters in Southeast Asian rainforests. Its fruits and seeds, which are recalcitrant and short-lived, are predated and dispersed by such as squirrels and birds including parrots, with often hoarding seeds to aid secondary dispersal. , particularly weevils and bark beetles, consume bark and leaves, while seed predators can inflict 40-90% damage, influencing regeneration dynamics and acting as natural population controls. As a , D. retusus supports a cascade of trophic interactions, sustaining pollinators, herbivores, and higher-order predators within these ecosystems. In terms of ecosystem services, mature stands of D. retusus-dominated forests sequester significant carbon, with estimates reaching approximately 218 tons per hectare in total carbon density, highlighting their role in climate regulation. The species' extensive root systems stabilize slopes by preventing soil erosion during heavy rains, while its canopy intercepts precipitation to regulate water flow and reduce nutrient leaching along riverine areas. These functions collectively enhance hydrological balance and soil health, positioning D. retusus as a foundational contributor to forest resilience in tropical landscapes.

Life Cycle Dynamics

Seeds of Dipterocarpus retusus are recalcitrant and germinate rapidly under shaded, moist conditions, typically within 2-4 weeks of dispersal, with optimal rates achieved at temperatures of 23-28°C. Germination percentages can reach up to 80% for seeds collected at peak maturity in early spring, declining to around 50% or less for later collections due to reduced viability. Seedlings establish in the forest understory, where they exhibit slow initial growth at rates of 10-20 cm per year in height, remaining highly shade-tolerant during this phase to persist under dense canopies for 1-2 years or longer before transitioning to greater light requirements for accelerated development. Juvenile trees grow steadily, achieving an average height increment of 50 cm per year and reaching approximately 10 m in 10-15 years under favorable conditions in secondary forests. Full maturity, marked by reproductive capability and canopy dominance, occurs after 50-80 years, during which increases at 0.5-1 cm annually, typically 0.7 cm in experimental settings. follows a mast fruiting pattern characteristic of dipterocarps, with synchronized, high-volume production every 3-5 years in aseasonal regions, interspersed by years of suppressed or absent fruiting to synchronize population-level events and satiate seed predators. In undisturbed forests, D. retusus exhibits longevity of 200-300 years, contributing to stable, uneven-aged structures driven by episodic during mast events rather than continuous regeneration. Such dynamics result in low densities of saplings and poles relative to mature trees, forming a non-reverse-J distribution typical of mixed dipterocarp stands. Populations are particularly susceptible to regeneration failures when overstory removal creates large canopy gaps, as prolonged shade is essential for early juvenile and establishment.

Uses

Timber and Resin

Dipterocarpus retusus yields a heavy timber with a ranging from 700 to 800 kg/m³ at 15% moisture content, classifying it as a moderately heavy to heavy wood suitable for structural applications. The heartwood is pale yellow to brown, with a straight grain and moderately coarse texture, contributing to its even working properties. This timber exhibits moderate natural durability against decay but is generally susceptible to and , requiring treatment for ground contact to enhance longevity in tropical conditions. The wood is extensively used in construction for beams, joists, and , as well as in where its strength supports durable hulls and components. In furniture production, it provides a stable material for frames and panels, while in , it serves as a primary source for manufacturing, particularly for structural grades. Heavy-duty applications, such as vehicle bodies, leverage its load-bearing capacity in regions like . The , known as , is extracted by the bark through incisions or holes made near the trunk base, typically 90-150 cm from the ground, with fire sometimes applied to stimulate flow; each tree yields under sustainable practices. This possesses high and an aromatic profile, attributed to its sesquiterpenoid essential oils, which confer fungicidal and termiticidal qualities. Resin applications include caulking for boats in and , where its properties seal hulls effectively. It is also processed into torches and candles for illumination, as well as varnishes for protecting boats, walls, and furniture surfaces. Medicinally, the resin is applied topically for and exhibits effects, supporting its traditional use in treating skin ailments and ulcers.

Cultural and Other Applications

In indigenous communities of , such as the Moran tribe, Dipterocarpus retusus holds sacred status, often protected within community forests and revered for its towering presence symbolizing resilience and endurance. Local traditions integrate the tree into rituals, reflecting its cultural role in spiritual practices among northeastern Indian ethnic groups. Additionally, the tree's wood serves as fuelwood in rural households, providing a reliable energy source in forested regions. The resin extracted from the trunk is applied topically in ethnomedicine to promote wound healing, leveraging its astringent and antiseptic qualities documented in traditional practices across Southeast Asia. Within the genus Dipterocarpus, species including D. retusus exhibit anti-inflammatory properties, with bark preparations historically used to alleviate rheumatism and joint pain in indigenous healing systems. Recent pharmacological studies on related Dipterocarpus species have identified antimicrobial activity in leaf extracts, attributing it to bioactive compounds like flavonoids and terpenoids that inhibit bacterial growth, suggesting potential for further ethnomedicinal applications. As the state tree of and , D. retusus embodies regional identity, adopted to highlight its ecological and cultural importance in northeastern . Beyond symbolism, the tree is planted ornamentally in gardens, parks, and along streets for its aesthetic appeal and expansive canopy, which provides cooling shade in urban and rural settings. In systems, it contributes to shade provision and , enhancing microclimates and nutrient retention in mixed plantations, as observed in enrichment planting trials in tropical forests.

Conservation

Status Assessment

Dipterocarpus retusus is classified as Endangered (EN) on the of , a designation first assigned in 1998 and reassessed on 24 February 2017 under criteria A2cd, reflecting an observed, estimated, inferred, or suspected population reduction of 50–70% over the past three generations attributable to habitat degradation and exploitation through . Populations are scattered and rare within its range, with the overall number continuing to decline due to ongoing pressures; this aligns with broader assessments of dipterocarp species facing severe threats across their range. The species' generation length is 100 years, placing the three-generation window at 300 years, during which the estimated 50–70% population reduction has occurred based on habitat loss models and historical data. The Endangered status was confirmed in a 2023 review of species. Regionally, conservation statuses vary: it is assessed as Endangered in , where populations are restricted to small areas in province and face strict protection measures, and in , where forest loss has severely impacted remaining stands. In , persistent risks from timber extraction continue despite protections in certain areas. In , particularly in northeastern states like where it serves as the state tree, it receives targeted protections.

Threats and Conservation Efforts

Dipterocarpus retusus faces significant threats from , primarily driven by selective logging targeting dipterocarps for high-value timber, which fragments forests and reduces population viability. Expansion of , particularly and plantation development, further exacerbates habitat loss in lowland tropical regions across its range. Infrastructure projects, such as dams along the River in , contribute to inundation and displacement of suitable habitats. Illegal resin tapping, a common practice for extraction in the Dipterocarpus genus, weakens tree vigor by damaging bark and reducing photosynthetic capacity, leading to increased susceptibility to disease and mortality. Secondary threats include , which alters rainfall patterns and increases stress in monsoon-dependent ecosystems, potentially shifting suitable habitats and hindering regeneration. In degraded areas, can outcompete native , while low natural regeneration is compounded by high rates from and vertebrates, such as long-tailed macaques, which consume up to 34% of pre-dispersal seeds in disturbed forests. These factors collectively contribute to declining populations, with ongoing monitoring indicating reduced seedling survival due to competition and environmental stressors. Conservation efforts prioritize in-situ protection within national parks, such as in , where D. retusus forms part of the dominant Dipterocarpus-Shorea forest and benefits from anti-poaching measures and habitat preservation. In Indonesia, Gunung Gede Pangrango National Park safeguards subpopulations through intact , with surveys showing higher seedling densities in undisturbed areas and minimal external threats. Reforestation initiatives in and involve planting over 1,000 seedlings annually in restoration sites, focusing on progeny trials to select resilient for degraded dipterocarp forests. Ex-situ conservation is supported by botanic gardens, including those at and , which maintain living collections and conduct research to preserve . Research and monitoring efforts include genetic studies assessing diversity through progeny trials in , aiding selection for and resilience to threats. In , community-based management programs engage indigenous groups in monitoring and sustainable harvesting, enhancing local stewardship and reducing illegal activities in buffer zones. These initiatives, combined with habitat suitability modeling, inform targeted restoration to mitigate ongoing declines.

References

  1. https://tropical.theferns.info/viewtropical.php?id=Dipterocarpus+retusus
  2. https://pmc.ncbi.nlm.nih.gov/articles/PMC11370694/
  3. https://www.iucnredlist.org/species/32400/2817693
  4. https://www.gbif.org/species/7299010
  5. https://www.ipni.org/n/320751-1
  6. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:14361-1
  7. https://www.mindat.org/taxon-6645.html
  8. https://www.stuartxchange.com/Apitong
  9. http://botanicalillustrations.org/species.php?id_species=350800
  10. https://powo.science.kew.org/taxon/320751-1
  11. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:320773-1
  12. https://www.worldfloraonline.org/taxon/wfo-0000651415
  13. https://www.nature.com/articles/s41598-019-48240-y
  14. https://www.cabidigitallibrary.org/doi/full/10.1079/cabicompendium.19740
  15. http://www.efloras.org/florataxon.aspx?flora_id=3&taxon_id=200014262
  16. https://www.flowersofindia.net/catalog/slides/Rusty%20Leaf%20Garjan.html
  17. https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:320751-1/general-information
  18. https://www.cifor-icraf.org/publications/pdf_files/Books/Dipterocarps.pdf
  19. https://ejournal.aptklhi.org/index.php/ijfr/article/download/517/177
  20. https://www.sciencedirect.com/topics/agricultural-and-biological-sciences/dipterocarpus
  21. https://pubmed.ncbi.nlm.nih.gov/21684899/
  22. https://www.cabidigitallibrary.org/doi/abs/10.5555/20023063054
  23. https://indianforester.co.in/index.php/indianforester/article/view/3258
  24. https://www.biosciencejournals.com/assets/archives/2018/vol6issue5/6-4-16-666.pdf
  25. https://www.plantsjournal.com/archives/2022/vol10issue4/PartA/10-3-15-578.pdf
  26. https://pmc.ncbi.nlm.nih.gov/articles/PMC6690942/
  27. https://www.researchgate.net/figure/Dipterocarpus-retusus-Blume-dipterocarpaceae_fig16_233639651
  28. https://www.fauna-flora.org/explained/forest-giants-preventing-the-downfall-of-the-dipterocarp/
  29. https://www.researchgate.net/publication/260098457_Ectomycorrhizal_Associations_of_the_Dipterocarpaceae
  30. https://ojs.nieindia.org/index.php/ijees/article/view/96
  31. https://www.researchgate.net/publication/316643989_Study_on_effect_of_time_of_seed_collection_on_germination_of_Dipterocarpus_retusus_Bl_Syn_D_macrocarpus_vesque
  32. https://www.researchgate.net/publication/324909111_Early_flowering_and_seed_setting_in_Dipterocarpus_retusus_a_new_report
  33. https://prosea.prota4u.org/view.aspx?id=3448
  34. https://www.iscientific.org/wp-content/uploads/2018/02/2-IJCBS-17-12-2.pdf
  35. https://www.researchgate.net/publication/271642103_A_Phytochemical_Ethnomedicinal_and_Pharmacological_review_of_genus_Dipterocarpus
  36. https://india.mongabay.com/2020/11/assams-tribal-communities-lost-land-and-forest-to-mining/
  37. https://www.econe.in/post/hollong-the-forgotten-tree
  38. https://pmc.ncbi.nlm.nih.gov/articles/PMC6751497/
  39. https://worldfornature.org/assam-st/
  40. https://worldfornature.org/arunachal-pradesh-st/
  41. https://www.tandfonline.com/doi/full/10.1080/21580103.2020.1831620
  42. https://www.bgci.org/wp/wp-content/uploads/2023/03/RL-Dipterocarpaceae-MedRes.pdf
  43. http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=200014262
  44. https://iopscience.iop.org/article/10.1088/1755-1315/457/1/012003
  45. https://www.researchgate.net/publication/369065737_The_Red_List_of_Dipterocarpaceae
  46. https://www.researchgate.net/publication/387974966_MaxEnt_modeling_for_habitat_suitability_assessment_of_threatened_Dipterocarpus_species_in_the_Indian_East_Himalayas
  47. https://pmc.ncbi.nlm.nih.gov/articles/PMC3179629/
  48. https://iopscience.iop.org/article/10.1088/1755-1315/457/1/012003/pdf
  49. https://english.icfre.gov.in/UserFiles/File/Annual-Report-2002-03/English/chap-5.pdf
  50. https://www.researchgate.net/publication/352345427_Ex-situ_conservation_effort_for_Dipterocarpus_spp_through_the_seedling_collection_and_nursery_management
  51. https://vafs.gov.vn/en/2006/09/an-early-assessment-of-dipterocarpus-retusus-progeny-trial/
  52. https://or.niscpr.res.in/index.php/IJTK/article/download/199/2763/38643
Add your contribution
Related Hubs
User Avatar
No comments yet.