Host tree association and canopy microhabitat characteristics of epiphytic orchids in Kanger Valley National Park, Chhattisgarh, India

Introduction

The family Orchidaceae represents one of the largest and most species-rich lineages of flowering plants, comprising over 28,000 species distributed globally across diverse terrestrial and canopy microhabitats (Chase et al., 2015; Zotz, 2016) [1,2] . Tropical forest ecosystems serve as primary centers of orchid diversity and speciation, hosting an immense variety of epiphytic forms that inhabit forest canopies (Dressler, 1993; Zotz, 2016) [3,2] . Unlike parasitic flora, epiphytic orchids utilize host trees-termed phorophytes-primarily as physical substrates for mechanical support without directly extracting water or metabolic nutrients from the host vascular tissue (Benzing, 1990) [4] . Moisture and essential inorganic nutrients are acquired from precipitation, atmospheric moisture, canopy drip, organic debris accumulation, and symbiotic associations with mycorrhizal fungi (Benzing, 1990; Zotz, 2016) [4,2] . Consequently, the establishment, spatial distribution, and long-term survival of epiphytic orchids depend heavily on phorophyte structural traits and canopy microclimates (Johansson, 1974; Callaway et al., 2002) [6, 5] . Bark physical properties, such as roughness, porosity, fissuring, and peeling rates, govern seed retention, germination success, root anchorage, and moisture conservation Callaway et al., 2002 [5] ; Adhikari et al., 2020) [7] . "Furthermore, canopy density directly modulates light availability, temperature fluctuations, and relative humidity gradients within the canopy strata (Benzing, 1990) [4] . Although many epiphytic orchids exhibit broad host ranges, host bias is frequently observed due to structural variations among phorophyte species (Wagner et al., 2015) [8] . Recent studies across tropical and subtropical forests emphasize that phorophyte size, bark characteristics, and canopy cover play crucial roles in shaping epiphytic assemblages (Seshadri et al., 2021; Timsina et al., 2024) [9,10] . Kanger Valley National Park (KVNP), situated in the Bastar region of Chhattisgarh, is a biodiversity hotspot characterized by a transition zone between Shorea robusta (Sal) and Tectona grandis (Teak) forests (Kotia et al., 2013; Jalal and Jayanthi, 2018) [12,11] The park exhibits high environmental heterogeneity, encompassing tropical moist deciduous, tropical dry deciduous, semi-evergreen, and limestone riverine habitats. While floristic surveys have recorded orchid species within KVNP, detailed investigations examining host tree relationships, host family associations, and associated microhabitat parameters remain limited. Understanding these ecological associations is critical for orchid conservation, as habitat fragmentation and the selective removal of mature phorophytes pose significant threats to orchid populations (Swarts et al., 2009) [13] . This study aimed to:

1. Document orchid species diversity and growth habits in KVNP.

2. Identify and document associated host tree species and host families.

3. Evaluate orchid species richness across different phorophytes.

4. Characterize associated microhabitats, including forest types, bark texture, and canopy density.

Survey methodology and taxonomic identification

Field surveys were conducted across representative forest compartments and microhabitats within KVNP during 2024-2025 and 2025-2026. A total of 19 orchid taxa were documented and assigned unique collection codes (CG-B-O1 to CG-B-O19). Plant growth habit (epiphytic vs. terrestrial) and growth pattern (monopodial vs. sympodial) were recorded for each species. Botanical identities were cross-referenced with standard regional floras and plant taxonomic databases (Kew Science, 2024) [14]

Peristylus goodyeroides

Terrestrial Sympodial None (Terrestrial / Forest Floor) N/A

CG-B-O16

Pholidota imbricata

Epiphytic Sympodial Ficus spp., Terminalia spp. Moraceae, Combretaceae

CG-B-O17

Rhynchostylis retusa

Host tree diversity and associations

Epiphytic orchids were documented on 13 distinct host tree species spanning 11 families. Among individual host species, Mangifera indica supported the highest orchid diversity (9 species). Ficus religiosa and Terminalia spp. (T. arjuna, T. elliptica, T. bellirica, T. chebula, T. tomentosa) each supported 6 orchid species. Syzygium cumini and Diospyros melanoxylon were each associated with 5 orchid species, while Shorea robusta and Schleichera oleosa supported 5 and 4 orchid species, respectively. At the host family level, Moraceae (Ficus religiosa, Ficus benghalensis, Ficus spp.), Anacardiaceae (Mangifera indica, Buchanania lanzan), and Combretaceae (Terminalia spp., Anogeissus latifolia) were associated with the highest overall orchid richness (10 orchid species each). Dipterocarpaceae (Shorea robusta) supported 8 species, while Myrtaceae (Syzygium cumini) and Ebenaceae (Diospyros melanoxylon) supported 6 species each.

Microhabitat and bark characteristics

Phorophytes characterized by rough, deeply fissured, or spongy bark (e.g., Mangifera indica, Terminalia elliptica, Ficus benghalensis, Shorea robusta) consistently hosted greater orchid species richness than hosts with smoother or flaking bark. Moist deciduous and semievergreen forest patches under dense-to-moderate canopy cover harbored the majority of epiphytic taxa (e.g., Acampe praemorsa, Aerides spp., Cymbidium aloifolium, Dendrobium spp.). In contrast, species such as Luisia trichorhiza, Vanda testacea, and Vanda tessellata were recorded in dry deciduous zones under open-to-moderate canopy cover.

Discussion

The strong dominance of epiphytic orchids (89.5%) in KVNP reflects the ecological suitability of the park's moist deciduous and semi-evergreen canopy microhabitats. Epiphytic preference for phorophytes such as Mangifera indica, Ficus species, and Terminalia species is closely related to bark morphology and microclimate (Callaway et al., 2002; Zotz, 2016) [5,2] . Rough, fissured, and porous bark provides physical micro-crevices that trap orchid seeds, retain organic humus, support mycorrhizal fungal colonization, and offer superior root anchorage (Benzing, 1990; Callaway et al., 2002) [4,5] . Furthermore, mature trees of Mangifera indica and Ficus species possess large canopy spreads that generate stable, high-humidity microclimates, buffering epiphytes against desiccation during seasonal dry periods. The high orchid richness associated with host families Moraceae, Anacardiaceae, and Combretaceae highlights their importance as structural foundation species in KVNP. Shorea robusta (Sal), despite being a dominant climax canopy tree in KVNP, supported fewer epiphytic species (8 species) compared to Mangifera indica (9 species). This may be attributed to the periodic bark shedding and resinous exudates of Sal, which can impede long-term epiphytic establishment relative to stable, non-exfoliating barks Johansson, 1974 [6] ; Gowland et al., 2021) [15] .

Variations in canopy openness also explain observed distribution patterns. Members of Dendrobium, Oberonia, and Pholidota were primarily restricted to dense, humid semi-evergreen and moist deciduous canopies, reflecting low drought tolerance. Conversely, Vanda species and Luisia trichorhiza occurred under open-to-moderate canopy conditions in dry deciduous patches. These taxa possess thick, coriaceous leaves, reduced surface-area-to-volume ratios, and well-developed velamen root structures adapted to withstand higher irradiances and lower relative humidity (Benzing, 1990; Zotz, 2016) [4,2] . The two terrestrial species (Geodorum densiflorum and Peristylus goodyeroides) occupied forest floor microhabitats with rich organic leaf litter, demonstrating that orchid diversity in KVNP spans both canopy and terrestrial niches. Because epiphytic orchids rely directly on mature host trees, forest management in KVNP must prioritize the preservation of large, mature phorophytes (Mangifera, Ficus, Terminalia, Syzygium) to ensure the long-term conservation of wild orchid populations (Swarts and Dixon, 2009; Seshadri et al., 2021) [13, 9] . Kanger Valley National Park (KVNP), situated in the Bastar region of Chhattisgarh, represents an ecologically important forest ecosystem characterized by diverse vegetation types and specialized habitats capable of supporting a rich orchid flora. Orchids exhibit remarkable ecological plasticity and occur in terrestrial as well as epiphytic forms. Epiphytic orchids utilize trees primarily as structural support and are influenced by host-tree characteristics, canopy structure, moisture availability and other microhabitat factors (Benzing, 1990; Dressler, 1993; Zotz, 2016) [4,3,2] . The present investigation was undertaken to document orchid diversity and assess the association of epiphytic orchids with their probable host trees and selected habitat characteristics in Kanger Valley National Park. A total of 19 orchid species were documented, comprising 17 epiphytic and two terrestrial species. The recorded epiphytic orchids included Acampe praemorsa, Aerides odorata, Aerides maculosa, Aerides multiflora, Cymbidium aloifolium, Dendrobium aphyllum, D. moschatum, D. transparens, D. nobile, D. herbaceum, Luisia trichorhiza, Pelatantheria insectifera, Oberonia falconeri, Rhynchostylis retusa, Pholidota imbricata, Vanda testacea and Vanda tessellata. The terrestrial orchids were Geodorum densiflorum and Peristylus goodyeroides. The epiphytic species showed associations with a diverse range of probable host trees, including Mangifera indica, Ficus religiosa, Ficus spp., Syzygium cumini, Shorea robusta, Terminalia spp., Schleichera oleosa, Diospyros melanoxylon, Azadirachta indica and Madhuca longifolia. Among the documented host trees, Mangifera indica was associated with the highest number of orchid species (9), followed by Ficus religiosa and Terminalia spp. (6 species each). At the host-family level, Moraceae and Anacardiaceae were associated with 10 orchid species each, followed by Combretaceae with eight species and Myrtaceae and Dipterocarpaceae with seven species each. Most epiphytic orchids were recorded in moist deciduous and semi-evergreen forest conditions and were associated predominantly with rough-barked host trees. Dense to moderate canopy conditions were associated with several orchid species, whereas Luisia trichorhiza, Vanda testacea and Vanda tessellata occurred under relatively open to moderate canopy conditions. The findings demonstrate that orchid occurrence in KVNP is associated with host-tree availability and forest structural characteristics. However, the present observations represent host association rather than statistically demonstrated host preference because quantitative data on total host availability were not available. Conservation of epiphytic orchids should therefore include protection of important host trees, mature forest structure, canopy heterogeneity and suitable microhabitats

Acknowledgements

Declaration of AI use

This manuscript was prepared through the combined contributions of all author(s), including contributions to the study design, data, content development, results, interpretation, and related scholarly work. The author(s) acknowledge the use of Grammarly and ChatGPT to assist with grammar checking, language refinement, reference formatting. These AI-assisted tools were not used as authors and did not replace the intellectual contributions or scholarly judgment of the author(s). All AI-assisted outputs, including content, references, and interpretations, were carefully reviewed, revised, verified, and approved by the author(s). The author(s) accept full responsibility for the accuracy, integrity, and final content of the manuscript.

Competing interests

Authors have declared that no competing interests exist

References

1. Chase MW, Cameron KM, Freudenstein JV, Pridgeon AM, Salazar G, van den Berg C, Schuiteman A. An updated classification of Orchidaceae. Botanical Journal of the Linnean Society. 2015;177(2):151-174.
2. Zotz G. Plants on Plants: The Biology of Vascular Epiphytes. Springer International Publishing, Switzerland; 2016.
3. Dressler RL. Phylogeny and Classification of the Orchid Family. Dioscorides Press, Portland, Oregon, USA; 1993.
4. Benzing DH. Vascular Epiphytes: General Biology and Ecophysiology. Cambridge University Press, Cambridge, UK; 1990.
5. Callaway RM, Reinhart KO, Moore GW, Moore DJ, Pennings SC. Epiphyte host preferences and host traits: mechanisms for species-specific interactions. Oecologia. 2002;132(2):221-230.
6. Johansson D. Ecology of vascular epiphytes in West African rain forest. Acta Phytogeographica Suecica. 1974;59:1-129.
7. Adhikari YP, Fischer A, Fischer HS. Microhabitat host tree specialization of epiphytic orchids in subtropical forests. Journal of Mountain Science. 2020;17(8):1921-1934.
8. Wagner K, Mendieta-Leiva G, Zotz G. Host specificity in vascular epiphytes: a review of methodology, modern concepts, and future directions. Biological Reviews. 2015;90(2):415-435.
9. Seshadri KS, Ganesh T, Devy MS. Determinants of vascular epiphyte assembly in the canopy of tropical wet evergreen forests, Western Ghats, India. Biotropica. 2021;53(4):1120-1132.
10. Timsina B, Rokaya MB, Münzbergová Z, Bhattarai KP. Host plant associations of epiphytic orchids along elevational gradients: implications for conservation under climate change. Plant Ecology. 2024;225(2):145-158.
11. Jalal JS, Jayanthi J. An annotated checklist of the orchids of western Himalaya, India. Lankesteriana. 2018;18(1):1-80.
12. Kotia A, Kumar P, Tiwari UL, Jalal JS, Prasad AN. Orchid diversity and distribution in Kanger Valley National Park, Chhattisgarh. Journal of Economic and Taxonomic Botany. 2013;37(1):207-215.
13. Swarts ND, Dixon KW. Terrestrial orchid conservation in the age of extinction. Annals of Botany. 2009;104(3):543-556.
14. Gowland KM, Wood JT, Clements MA, Nicotra AB. Significant host tree preferences in epiphytic orchids. Functional Plant Biology. 2021;48(4):412-425. International Journal of Research in Agronomy https://www.agronomyjournals.com 26180618, 2026, 9(9), Downloaded from https://www.doi.org/10.33545/2618060X.2026.v9.i9Sf.6671 by International Journal of Research in Agronomy on [01/10/2026]. See the Terms and Conditions (https://www.agronomyjournals.com) for rules of use; OA articles are governed by the applicable Creative Commons License
15. Rasmussen HN. Terrestrial Orchids: From Seed to Mycorrhizal Plant. Cambridge University Press, Cambridge, UK; 1995. How to cite this article: Gautam S, Sahu R, Sahu TL, Sao B, Singh R, Tiwari S, et al. Host tree association and canopy microhabitat characteristics of epiphytic orchids in Kanger Valley National Park, Chhattisgarh, India. International Journal of Research in Agronomy. 2026;9(9):489-497. doi: https://www.doi. org/10.33545/2618060X.2026.v9.i9Sf.6671