Plant diversity and vegetation composition of the Chilphi range, Kawardha forest division, Chhattisgarh

Introduction

Tropical forests are among the most structurally complex and species-rich ecosystems on Earth and exhibit substantial heterogeneity even across small spatial scales (Sullivan et al., 2017) [1] . Understanding this plant diversity and vegetation composition is fundamental to the conservation and sustainable management of these critical ecosystems. Floristic surveys serve as a primary tool in this endeavor, providing essential data not only on species richness but also on ecological stability, successional stages, and the impacts of anthropogenic disturbance on vegetation dynamics (Chiarucci A & Bonini, 2005; Nicholas et al., 2006) [2,3] . In India, tropical dry deciduous forests constitute a major portion of the country's forest cover, recognized for their ecological significance and substantial resource value (Champion & Seth, 1968; Bahuguna et al., 2016) [4,5] . These forests harbor a wide variety of timberyielding, medicinal, and non-timber forest product (NTFP) species that sustain the livelihoods of rural and tribal communities, thereby contributing to both biodiversity conservation and socio-economic resilience. The state of Chhattisgarh is characterized by a mosaic of such forest types, among which dry deciduous formations are the most extensive. The Kawardha Forest Division, forming part of the biodiverse Maikal Range, supports Sal dominated vegetation with notable floristic diversity. Previous studies in central India have documented considerable variation in forest composition across different regions, attributed to differences in topography, soil characteristics, and varying degrees of anthropogenic pressure (Dutta & Devi, 2017; Lal et al., 2022; Panda et al., 2023) [6,7,8] . However, despite its ecological importance, systematic and quantitative studies on the species composition and diversity of the Kawardha Forest Division remain limited. The Chilphi Range within this division represents a significant but understudied landscape. Documenting the floristic composition of such lesserexplored areas is crucial for understanding regional biodiversity patterns and for developing effective, sitespecific conservation strategies. In this context, the present study was conducted to document and analyze the plant species composition and diversity of the Chilphi Range. The study also seeks to evaluate spatial variation in vegetation structure across four zones-north, south, east, and west, representing distinct vegetation conditions within the landscape. The findings are expected to contribute to baseline ecological knowledge essential for long-term forest monitoring, biodiversity assessment, and sustainable management planning in central India's dry deciduous ecosystems.

Materials and Methods

Study Area

The study was conducted in the Chilphi Range of the Bhoramdev Wildlife Sanctuary, Kawardha Forest Division, Chhattisgarh, India (21°57'-22°15'N; 80°53'-81°10'E). The site covers an area of 192 km², located approximately 148 km from Raipur. Geographically, it forms part of the Maikal hills within the Central Indian Highlands. The landscape is topographically diverse, with elevations ranging from 320 to 925 meters above sea level and experiences a subtropical climate with a mean annual temperature range of 21.6-33.6 °C and occasional winter frost. This varied environment supports a rich biodiversity, including three distinct forest types: Dry Teak Forest (5A/C1b), Moist Peninsular High-Level Sal Forest (3C/C2e(i)), and Southern Dry Mixed Deciduous Forest (5A/C3).

Fig 1: Map of the Study Area

Methods of Data Collection and Analysis

Field sampling was conducted between 2023 and 2024. Following an initial reconnaissance survey, the study area was stratified into four cardinal zones (North, South, East, and West) to ensure comprehensive spatial coverage. Within each zone, vegetation was sampled using a nested-quadrat approach. Ten 10 m × 10 m quadrats were established for the enumeration of trees. The Girth at Breast Height (GBH) of every individual tree was measured at 1.37 m above ground level and subsequently converted to Diameter at Breast Height (DBH) for analysis. Concentrically nested within each major quadrat, a 5 m × 5 m sub-quadrat was established for shrub sampling, and a 1 m × 1 m sub-quadrat was established for herbs. The collar diameter was recorded for every individual shrub and herb within their respective sub-quadrats. The collected vegetation data were quantitatively analyzed for frequency, density, and abundance (Curtis & McIntosh, 1950) [9] . The Importance Value Index (IVI) was calculated as the sum of relative frequency, relative density, and relative basal area (Phillips, 1959) [10] . Plant diversity across the different layers and zones was assessed using Shannon Index (Shannon and Weaver, 1963) [11] , Simpson's Index of Dominance (Simpson, 1949) [12] , Pielou's Evenness Index (Pielou, 1966) [13] , Species richness (Margalef, 1958) [14] and Beta Diversity (Whittaker, 1972) [15] .

Results

Species Composition of Chilphi Range

A total of 63 plant species belonging to 58 genera and 34 families were recorded from the study area. Of these, 28 were trees (26 genera and 20 families), 15 shrubs (14 genera and 12 families), and 20 herbs (19 genera and 11 families). The family Fabaceae contributed the highest number of species (8), followed by Combretaceae (4) and Asteraceae (4).

Tree Layer

The tree species composition varied markedly across the four cardinal zones of the study area (Table 1). Total stem density was highest in the North zone (980 stems ha⁻¹), followed by the West (940 stems ha⁻¹), while the South and East zones were less densely stocked (730 and 710 stems ha⁻¹, respectively). In contrast, the East zone possessed the greatest stand basal area (48.69 m² ha⁻¹), while the West, North, and South zones exhibited remarkably similar basal areas as 42.10 m² ha⁻¹, 42.25 m² ha⁻¹ and 42.42 m² ha⁻¹ respectively. This discrepancy indicates that the East zone was characterized by fewer but larger trees, whereas the North zone comprised a higher number of smaller-diameter individuals. A few key species dominated the study area, as reflected by the Importance Value Index (IVI). Shorea robusta consistently achieved the highest Importance Value Index (IVI) in the West (95.24), North (170.05), and South (105.36) zones. Its dominance was particularly pronounced in the North zone, where its stem density and basal area were 630 stems ha⁻¹ and 32.62 m² ha⁻¹ respectively, indicating a near-monospecific stand structure. In the East zone, however, Diospyros melanoxylon was the most important species with IVI as 58.26. Despite this, the stand structure was still influenced by larger individuals of Shorea robusta and Anogeissus latifolia, which recorded the highest basal areas in that zone (12.57 and 9.01 m² ha⁻¹, respectively). The West zone supported the highest number of tree species (16 species), followed by the East zone (10 species). Across all zones, low-density species such as Cassia fistula, Bauhinia roxburghiana, and Schrebera swietinioides occurred sporadically, contributing little to total basal area and IVI but enhancing overall species diversity. Abbreviations: F = Frequency (%), D = Density (stems ha -1 ), BA = Basal area (m 2 ha -1 ) and IVI = Importance value index

Shrub Layer

Shrub composition varied across the four zones of the Chilphi Range ( Abbreviations: F = Frequency (%), D = Density (stems ha -1 ), BA = Basal area (m 2 ha -1 ) and IVI = Importance value index

Herb Layer

Herbaceous species composition showed considerable variation across the four zones of the Chilphi Range (

Diversity Analysis

The diversity indices of tree, shrub, and herb layers exhibited notable spatial variation across the four zones of the Chilphi Range (Table 4). The Shannon diversity index (H′) for trees ranged from 1.43 to 2.98, being highest in the east zone and lowest in the north. Shrubs showed moderate variation (1.40-2.25), with the west zone showing the highest diversity, while herbs displayed the widest range (1.88-3.02), attaining maximum diversity in the north zone. Simpson's dominance index (Cd) for trees varied between 0.15 and 0.61, indicating maximum dominance in the north and minimum in the east zone. Shrub dominance ranged from 0.26 to 0.46, being highest in the east and lowest in the west, whereas for herbs, it varied between 0.15 and 0.32, with the greatest dominance in the east zone. Equitability (e) values for trees ranged from 0.54 to 1.30, with the east and south zones showing a more even distribution of individuals among species. Shrubs showed relatively uniform evenness (0.78-1.10), while herbs exhibited consistently high values (0.96-1.18), indicating a fairly even species distribution across zones. Margalef's species richness index (d) for trees ranged from 9.77 to 15.78, being highest in the west zone and lowest in the east. Shrubs followed a similar pattern, with richness values between 3.72 and 9.74, and herbs between 6.77 and 14.77, the latter being highest in the south zone. Beta diversity (β) values indicated considerable habitat heterogeneity. For trees, β ranged from 2.94 to 5.00, with the south zone showing the highest heterogeneity. Shrub β values (5.00-6.67) were maximum in the west, whereas herb β (2.59-4.48) peaked in the north zone. Overall, diversity and richness were highest in the east and west zones, while dominance was most pronounced in the north, reflecting clear ecological differentiation across the study area. Abbreviations: F = Frequency (%), D = Density (stems ha -1 ), BA = Basal area (m 2 ha -1 ) and IVI = Importance value index [16] Tropical Dry Deciduous Forest, Achanakmaar Amarkantak Biosphere Reserve (AABR) Tree 2.36-2.91 0.21-0.37 0.77-1.01 5.13-6.13 3.33-4.56 Lal et al., (2022) [7] Dry Tropical Forest, Achanakmaar Amarkantak Biosphere Reserve (AABR) Herb 2.18-3.64 0.045-0.17 0.81-0.95 16.69-30.52 3.12-7.36 Thakur (2018) [17] Tropical Dry Deciduous Forest, Jharsuguda, Odisha Tree 3-3.45 0.05-0.08 0.86-0.88 --Mansingh et al., (2025) [18] Tropical Moist Deciduous Forest, Similipal Biosphere Reserve, Odisha [6,8] . The predominance of Fabaceae and Combretaceae among trees reflects their wide ecological amplitude and adaptation to seasonal drought (Lal et al., 2022) [7] , while the herbaceous dominance of Asteraceae and Poaceae suggests secondary successional stages influenced by recurring fire and grazing pressures. Spatial variation in density and IVI across zones reflects the mosaic character of the landscape and management history. The North zone exhibited a Sal-dominated composition typical of relatively closed Sal stands, the South zone combined Sal dominance with teak plantations, the West zone comprised Sal-mixed forest and the East zone consisted of mixed forest interspersed with dry grasslands. These structural differences explain observed patterns in density and IVI. Shorea robusta dominates most zones due to its regeneration capacity under disturbance, while the East zone's mixed composition ( [8,22,18] but lower than those reported from moist deciduous forests (Mishra et al., 2012; Dutta & Devi, 2017; Kumar & Saikia, 2020) [19,6,21] , where higher rainfall and humidity promote vigorous tree growth and greater stand biomass. The relatively moderate basal area and density recorded in the present study are characteristic of seasonally dry environments where fire, grazing, and resource extraction restrict regeneration and tree girth increment. Shrub density (1440-2480 shrubs ha⁻¹) was consistent with reports from Bhoramdeo Wildlife Sanctuary (Jhariya, 2017) [23] , though basal area was comparatively lower. The widespread occurrence of Vernonia divergens, Colebrookea oppositifolia, and Lantana camara indicates partial invasion, suggesting the need for management to restore native understorey diversity. Herb density and basal area were relatively lower than those reported by Panda et al. (2020) [20] and Dutta & Devi (2017) [6] , likely due to frequent fires and lateritic soils that limit herb regeneration. The Shannon diversity index (H′) for trees (1.43-2.98) corresponds with values reported from dry tropical forests of Korba (Mexudhan et al., 2024) [16] , Ranchi (Panda et al., 2023) [8] , and Achanakmaar-Amarkantak Biosphere Reserve (Lal et al., 2022) [7] , though lower than moist deciduous forests of Assam (Dutta & Devi, 2017) [6] . Moderate to high heterogeneity was observed in shrubs and herbs, with an inverse relationship between tree canopy density and herb diversity, suggesting that dense stands reduce understorey light penetration and thereby limit herbaceous growth. The inverse trend between Shannon and Simpson indices further confirms the absence of extreme dominance, particularly in the herb layer. Equitability (0.54-1.30 across layers) and species richness (3.72-15.78 across layers) indicate a balanced community structure typical of semi-disturbed dry deciduous systems. Beta diversity values (2.94-5.00 for trees; 5.00-6.67 for shrubs; 2.59-4.48 for shrubs) denote considerable species turnover and habitat heterogeneity, comparable to other studies from Korba and AABR (Lal et al., 2022; Mexudhan et al., 2024) [7,16] . This variability reflects the mosaic landscape character of the Chilphi Range, shaped by microclimatic and disturbance gradients. Overall, the Chilphi Range sustains a relatively intact Saldominated forest with diverse understorey vegetation, functioning as an important ecological corridor adjoining the Kanha Tiger Reserve. Targeted management focusing on fire control, invasive species removal, and enrichment planting of native species could further enhance its ecological resilience and biodiversity value.

Conclusion

The Chilphi Range of the Kawardha Forest Division represents a characteristic tropical dry deciduous forest of central India, predominantly composed of Shorea robusta with associates such as Terminalia tomentosa, Diospyros melanoxylon, and Anogeissus latifolia. Variation in species composition and structural attributes among the four zones reflects the combined influence of edaphic factors, canopy cover, and human disturbance. The East and West zones exhibited relatively higher species diversity and evenness, whereas the North zone was dominated by Sal, and the South zone represented a Sal-Teak mixed formation. Moderate tree density and basal area values indicate a stable yet disturbance-influenced ecosystem where recurrent fire and grazing constrain regeneration. The shrub and herb layers showed notable heterogeneity and partial invasion, suggesting altered successional dynamics. Overall, the Chilphi Range maintains substantial floristic diversity and ecological significance, serving as a vital transitional corridor adjoining the Kanha Tiger Reserve. Effective management focusing on fire prevention, invasive species control, and enrichment of native flora is crucial for sustaining its ecological resilience.

Acknowledgement

AcknowledgementsThe authors are highly thankful to Mr. Shashi Kumar (DFO), Kawardha Forest Division and all the forest staff for providing necessary facility needed to conduct the experiment in natural forest area.

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