11 Vegetation, as an indicator, plays a pivotal role in evaluating the health and stability of the ecological environment, and primarily reflects the way ecological systems respond to both climate change and human disturbances (Huo & Sun, 2021; Zhang & Ye, 2021). Vegetation provides a wide range of benefit to humankind, commonly known as ecosystem services (Reid et al., 2005). These include carbon storage regulating the global climate (Mitchard, 2018), an important role in water regulation and soil conservation (Zhang & Ye, 2021) and the support of rural livelihoods in communities with high dependencies on natural resources (Asprilla- Perea & Díaz-Puente, 2019). National parks and other similarly managed reserves contribute to addressing climate change and fostering development (Dimobe et al., 2019). Additionally, protected areas are outstanding in terms of their richness and abundance of species and provision of multiple ecosystem services Banko Janakari, Vol 33 No. 2, 2023 Pp 11‒23https://doi.org/10.3126/banko.v33i2.55086 Plant communities in Shivapuri-Nagarjun National Park, Central Nepal This study analyzes the plant communities in the Shivapuri-Nagarjun National Park (SNNP), Nepal. Field survey was carried in the national park using quadrat sampling at four different sites selected based on elevation and aspects. Diversity indices, density, frequency, abundance and importance value index (IVI) were measured for tree species. A total of 31 tree species representing 29 genera and 18 families were reported from the SNNP. Four types of plant communities (Schima-Pinus- Alnus community, Schima-Lindera mixed community, Schima-Castanopsis mixed community, and Quercus-Myrsine-Rhododendron mixed community) characterized with elevation and aspects were identified by cluster analysis. The Panimuhan Site situated on the south-west aspect at lower elevation was rich in terms of number of tree species. The IVI value of Castanopsis tribuloides in the Sundarijal Site showed the highest density and IVI. The Quercus species occurring at the Bagdwar Site at higher elevation was found to be the dominant trees with higher diameter (DBH) values. Schima wallichii and Rhododendron arboreum showed their association with different species in both the eastern and western aspects. Tree canopy, litter cover and shrub cover showed significant effect on species composition whereas herb cover and rock cover showed no effect on species composition. This study is expected to contribute in understanding the present vegetation status and diversity of SNNP, which could be helpful in implementing sound management planning to boost conservation of ecosystems and biodiversity. Keywords: Diversity index, Shivapuri-Nagarjun National Park, species composition, vegetation T. M. Dhakall, 2 , L. B. Thapa2 , R. K. P. Yadav2 , and C. P. Pokhrel2* Received: 22, May 2023 Revised: 7, December 2023 Accepted: 4, February 2024 Published: 26, February 2024 1 Siddhanath Science Campus, Tribhuvan University, Mahendranagar, Kanchanpur, Nepal 2 Central Department of Botany, Tribhuvan University, Kirtipur, Kathmandu. * E-mail: chandra.pokhrel@cdb.tu.edu.np https://orcid.org/0000-0002-4764-4554 https://orcid.org/0000-0003-3513-2276 https://orcid.org/0000-0001-5787-3134 https://orcid.org/0000-0003-2573-8370 mailto:chandra.pokhrel@cdb.tu.edu.np Banko Janakari, Vol 33 No. 2 12 Dhakal et al. (Harrison et al., 2014; Baccini et al., 2017). These areas serve as crucial sinks with the capacity to absorb substantial amounts of carbon dioxide from the atmosphere (Dimobe et al., 2019). Globally, protected areas store an average of 115 Mg ha−1 of carbon in above-ground biomass, which is higher than the average global estimate (71.6 Mg ha−1) (FAO, 2010; Pandey, 2012). Changes in the composition and structure of vegetation, instigated by both climatic and human-induced disturbances, can result in shifts in species diversity and associated carbon stocks (Dimobe et al., 2019). Owing to its wide range of physiographic and climatic variations as well as unique ecological setting, Nepal, a mountainous country, is an important Himalayan region in terms of ecosystem, vegetation and biodiversity where 118 ecosystems and 75 vegetation types were reported (Dobremez, 1970; GON, 2014). On the basis of climate, vegetation & floristic composition, the country’s forests are classified into 35 types (Stainton, 1972). Nepal’s topographical and climatological variations taken together with other local factors account for the high species richness within the country. Despite small land surface (0.1 % of the world’s total land area), Nepal represents over 3 % of the world’s known flora, of which 284 are endemic ones (GON, 2014). Nepal’s forest including other wood land occupies a total of 44.74 %. Out of the total forest area, 37.80 % lies in the Middle Mountains, 32.25 % in High Mountains & High Himal, 23.04 % in Churia Hills, and 6.90 % in Terai (DFRS, 2015). Similarly, protected areas cover 23.56 % of the country’s total area encompassing 12 national parks, six conservation areas, 13 buffer zones areas, one wildlife reserve and one hunting reserve (DNPWC, 2019). Among the national parks, the Shivpuri-Nagarjun National Park (SNNP) with an area of 159 sq. km, lies in the sub-tropical and lower temperate zone and presents sole repository of the middle mountain’s flora, fauna and ecosystem. It is located towards the north-eastern part of the Kathmandu Valley within Bagmati Province of central Nepal. The SNNP is one of the major fresh water sources for the Kathmandu Valley. Apart from that, the area possesses historical, religious, cultural, touristic, environmental, and archeological significance. Therefore, understanding the present vegetation status and diversity of the area is essential for sound management planning, thereby conserving ecosystem and biodiversity. Previous studies in the SNNP reported vegetation structure in a particular region of the park. For example, a study on quantitative analyses of vegetation (trees and shrubs) was undertaken on the north-east (NE) and south-west (SW) slopes of the Nagarjun hill (Yadav & Sah, 1998). Sigdel (2008) studied the vegetation structure along altitudinal bands in the Shivapuri National Park. Other studies are focused mainly on specific species such as Adiantum (Singh & Siwakoti, 2012) and the phyllospheric bacterial populations of the woody vegetation within the park (Yadav et al., 2013). This study aims to characterize the plant communities in the SNNP focusing mainly on tree species, and produce baseline information for community structure, diversity, and ecology that would be helpful for developing sustainable forest management strategy and conserving natural resources. Materials and methods Study sites The study was conducted in the Shivpuri- Nagarjun National Park (SNNP) situated within the Bagmati Province of Nepal in 2020 (Figure 1). The national park is situated between 27°43' - 27°52' N latitudes and 85°13' - 85°30' E longitudes towards the north-eastern part of the Kathmandu Valley, and covers a total area of 159 sq km (SNNP, 2022). The elevation of the terrain ranges from 1350 m to 2795 m above the mean sea level (msl). Geographically the national park represents a transitional zone between subtropical and temperate regions. The mean annual rainfall of the SNNP is 2727 mm (SNNP, 2022). The rainy season start from June and ends by October whereas the dry season starts from November and ends by April. The temperature varies from 27.7o C to 0.30o C (SNNP, 2022). The vegetation of the area is characterized as subtropical and temperate. The subtropical zone is dominated by species such as Schima wallichii, Castanopsis indica, C. tribuloides and Pinus roxburghii. The mixed temperate forest at higher elevations Banko Janakari, Vol 33 No. 2 13 Dhakal et al. consists of Quercus lanata, Q. semecarpifolia and Rhododendron arboreum as dominant species (Sigdel, 2008). Vegetation sampling and data collection The study was conducted in 2020 during post- monsoon season. A total of 43 sample plots (quadrats), each of size 10×10m2 were sampled at the south-eastern and south-western aspects and also at the top of the national park. Among those, 13 sample plots were within the Sundarijal Site (SS) located at an elevation between 1514- 1634 m above the msl towards the eastern aspect while 9 plots were within the Panimuhan Site (PS) located between 1731-1869 m above the msl towards the south-western aspect. Similarly, 9 plots were sampled in the Okhreni Site (OS) located between 1883-1945m above the msl nearby the Okhreni Village within the national park. The remaining 12 sample plots were in the Bagdwar Site (BS) at the top of the national park (elevation between 2244-2795m above the msl). This site is dominated by Quercus species, and a sacred "Bagdwar Temple" exists within the site. Three to four plots were at a spacing of 100m along each of the three transects were established parallelly at a spacing of 150-200m in each site and there were 3-4 plots at a spacing of 100m in each transect. The locations of the sample plots are presented in Figure 1. All the individual tree species in each plot were counted, and herbs, shrubs and climbers were also duly recorded. The density, frequency, total basal area, relative values of density, frequency, abundance, and DBH (diameter of breast height) of the tree species were calculated following Misra (1968), Muller-Dombois & Ellenberg (1974), and Zobel et al. (1987). Per hectare density and basal area were also calculated for all the tree species. Besides, the Importance Value Indices (IVIs) of the tree species were determined by summing up the values of relative of density (RD), relative frequency (RF), and relative dominance (RDo). The Shannon-Wiener Index, Simpson Index for species diversity and Pielou Evenness were computed following Shannon & Wiener (1963), Whittaker (1975) and Pielou (1975). The tree canopy cover, shrubs, herbs, rocks and litter in each plot were estimated visually as a percentage cover. The plant species were identified by following Malla et al. (1986), Rajbhandari et al. (2021) and Shrestha et al. (2022). Voucher specimens were deposited at the Tribhuvan University Central Herbarium (TUCH), Kirtipur, Kathmandu, Nepal. Statistical analysis Multivariate analysis (ordination) was applied for knowing the effects of environmental variables (tree canopy, cover of shrubs, herb, litter, and rock) on species composition. All the species of herbs, shrubs and trees were included in the analysis. The gradient length in the data yielded through Detrended Correspondence Analysis (DCA) was 4.8; therefore, Canonical Correspondence Analysis (CCA) was used as a unimodal technique. The data were down-weighted so as to reduce the effect of rare species in the result. Besides, Permutational Multivariate Analysis of Variance (PERMANOVA) was used to test the significance of the relationships. Hierarchical Clustering Analysis (CA) based on Sørensen Similarity Index was applied to identify plant Figure 1: Map showing study area and sampling locations in the SNPP (BS = Bagdwar Site, OS = Okhreni Site, SS = Sundarijal Site, and PS = Panimuhan Site) Banko Janakari, Vol 33 No. 2 14 Dhakal et al. communities. Average linkage clustering based on minimum average distance between groups was used, and a 'hierarchical cluster dendrogram' was generated. The analyses were performed using the R Software (version 3.5.1) (R Core Team, 2018). Results Floristic composition A total of 31 tree species from 29 genera and 18 families were reported from the study sites. The families Fagaceae and Rosaceae had 4 species each followed by Lauraceae, Theaceae and Myrsinaceae with 3 species each. Similarly, Betulaceae and Ericaceae were represented by 2 species each while the rest of the families by single species (Table 1). The Panimuhan Site (PS) was rich in terms of number of species (22 species) followed by the Sundarijal Site (SS) with 17 species, the Okhreni Site (OS) with 12 species and the least number of tree species (11 species) were reported from the Bagdwar Site (BS, Table 1). Among the 22 species reported from the Panimuhan Site (PS), Albizia julibrissin, Betula alnoides, Castanopsis indica, Eurya acuminata, Fraxinus floribunda, Prunus cerasoides, Pyrus pashia, and Saurauia napaulensis were limited in this site (Table1). The tree Ziziphus incurva was confined in the Okhreni Site (OS) and Cinnamomum tamala, Edgeworthia gardneri, Grevillea robusta and Lindera pulcherrima were confined in Bagdwar Site (BS). The trees Garuga pinnata, Heptapleurum rhododendrifolium and Woodfordia fruticosa were found only in the Sundarijal Site (SS). Altogether, 6 species were found to be common in the Bagdwar and Panimuhan Sites. Similarly, 11 species were common in Okhreni and Sundarijal sites whereas 5 species were common in all the study sites (Table 1). Table 1: Plants found in different sites of the SNNP S. N. Species name Plant type Family Sites 1. Albizia julibrissin var. mollis (Wall.) Benth. Tree Fabaceae PS 2. Alnus nepalensis D. Don Tree Betulaceae SS, PS 3. Betula alnoides Buch.-Ham. ex D. Don Tree Betulaceae PS 4. Castanopsis tribuloides (Sm.) A. DC. Tree Fagaceae OS, SS, PS 5. C. indica (Roxburgh ex Lindley) Tree Fagaceae PS 6. Cinnamomum tamala (Buch.-Ham.) T. Nees & Nees Tree Lauraceae BS 7. Edgeworthia gardneri Meisn. Small Tree/Shrub Thymelaeaceae BS 8. Rhaphiolepis dubia (Lindl.) B. B. Liu & J. Wen Small Tree/Shrub Rosaceae OS, SS, PS 9. Eurya acuminata DC. Tree Theaceae PS 10. E. japonica Thunb. Tree Theaceae BS, OS, SS, PS 11. Fraxinus floribunda Wall. Tree Oleaceae PS 12. Garuga pinnata Roxb. Tree Burseraceae SS 13. Grevillea robusta A. Cunn. ex R. Br. Tree Proteaceae BS 14. Lindera nacusua (D. Don) Merr. Tree/Shrub Lauraceae OS, SS, PS 15. L. pulcherrima (Nees) Hook. f. Small Tree Lauraceae BS 16. Lyonia ovalifolia (Wall.) Drude Small Tree/Shrub Ericaceae BS, OS, SS, PS Banko Janakari, Vol 33 No. 2 15 Dhakal et al. S. N. Species name Plant type Family Sites 17. Morella esculenta (Buch.-Ham. ex D. Don) I. M. Turner Tree Myricaceae SS, PS 18. Myrsine capitellata Wall. Tree Myrsinaceae BS, OS, SS, PS 19. M. semiserrata Wall. Tree Myrsinaceae BS, OS, SS, PS 20. Pinus roxburghii Sarg. Tree Pinaceae OS, SS, PS 21. Prunus cerasoides Buch. Ham. ex D. Don Tree Rosaceae PS 22. P. nepalensis Ser. Tree Rosaceae PS 23. Pyrus pashia Buch. Ham. ex D. Don Tree Rosaceae OS, SS, PS 24. Quercus lamellosa Sm. Tree Fagaceae BS, PS 25. Q. semecarpifolia Sm. Tree Fagaceae BS, SS, 26. Rhododendron arboreum Sm. Tree Ericaceae BS, OS, SS, PS 27. Saurauia napaulensis DC. Tree Actinidiaceae PS 28. Heptapleurum rhododendrifolium (Griff.) G. M. Plunkett & Lowry Tree Araliaceae SS 29. Schima wallichii (DC.) Korth. Tree Theaceae OS, SS, PS 30. Woodfordia fruticosa (L.) Kurz Small Tree Lythraceae SS 31. Ziziphus incurva Roxb. Tree Rhamnaceae OS Note: BS = Bagdwar Site; OS = Okhreni Site; PS = Panimuhan Site; and SS = Sundarijal Site. Diversity and importance value indices of tree species Based on the diversity indices, the Panimuhan Site was found to be more diverse than other sites. The order of the Simpson Diversity Index and Shanon-Weiner Index values were: PS>OS>BS>SS (Table 2). Similarly, the Pielou's Evenness also followed the same pattern as the diversity indices. Table 2: Diversity indices and evenness at different sites Index/Evenness Sites PS OS BS SS Simpson Index 0.90 0.89 0.79 0.73 Shannon-Weiner Index 2.50 2.36 1.86 1.79 Pielou's Evenness 0.50 0.47 0.36 0.32 Quercus semecarpifolia had the highest IVI value (103.55) in the Bagdwar Site, with 24.11 relative density and 15.58 relative frequency, but the relative density was high in M. semiserrata (34.75). Q. semecarpifolia was also present in the Sundarijal Site, but its IVI was <10. Comparing the values of the IVI among the species in the Bagdwar Site, M. semiserrata, R. arboreum, and M. capitellata were found to be the species having the IVI >25 (Table 3). M. semiserrata had the IVI value of 26.19 in the Okhreni Site while the values were >5 in the other two sites viz. Sundarijal and Panimuhan. R. arboreum had the IVI value of 25.05 in the Sundarijal Site following the Bagdwar Site whereas the values were less (>10) in the Panimuhan and Okhreni sites (Table 3). Similarly, M. capitellata was present in the other three sites besides the Bagdwar Site with the IVI values ranging from 12.42 to 35.20. Among the species having the least IVI in the Bagdwar Site, Banko Janakari, Vol 33 No. 2 16 Dhakal et al. G. robusta was not found in the other sites while L. ovalifolia had almost the similar IVI value in the Sundarijal Site, but the values were higher in the Panimuhan (14.51) and Okhreni (20.46) sites than in the Bagdwar Site (4.33, Table 3). The tree species in the Okhreni Site had the IVI values ranging from 2.62 (R. arboreum) to 47.54 (L. nacusua). S. wallichii, P. pashia, P. roxburghii had the IVI values of 44.61, 33.46, and 31.38, respectively. Z. incurva was the species having comparatively the least IVI (6.50) in the Okhreni Site. L. nacusua was also present in the Sundarijal and Panimuhan sites with low density and frequency as compared to those in the Okhreni Site. The density and frequency of S. wallichii were higher in the Panimuhan Site with the IVI value of 66.37 but lesser in the Sundarijal Site than in the Okhreni Site (Table 3). P. pashia and P. roxburghii were also reported in Sundarijal and Panimuhan sites. P. pashia had less than 5 relative density and relative frequency in both the Sundarijal and Panimuhan sites, but P. roxburghii had much higher IVI value of 15.59 in the Sundarijal Site and 27.12 in the Panimuhan Site (Table 3). Among all the tree species, C. tribuloides was the dominant at the Sundarijal Site with the highest IVI value of 120.05 followed by Panimuhan site (40.09) and Okhreni site (16.21). E. acuminata, G. pinata, W. fruticosa, P. pashia, A. nepalensis and M. semiserrata were among the species having the least IVI (<5) at the Sundarijal Site (Table 3). Following S. wallichii and C. tribuloides, A. nepalensis had the IVI value of 29.63 at the Panimuhan Site. The tree species- A. julibrissin, C. indica and S. napaulensis were found only at the Panimuhan Site with the relative density, frequency, and dominance less than 2 and the IVI less than 3 (Table 3). Table 3 : Relative Density (RD), Relative Frequency (RF), Relative Dominance (RDo), and Importance Value Index (IVI) of tree species in different sites of SNNP S. N. Name of species Bagdwar Site (BS) Okhreni Site (OS) Sundarijal Site (SS) Panimuhan Site (PS) RD RF RDo IVI RD RF RDo IVI RD RF RDo IVI RD RF RDo IVI 1. A. julibrissin - - - - - - - - - - - - 0.39 1.67 0.40 2.46 2. A. nepalensis - - - - - - - - 0.56 1.85 1.25 03.66 6.98 6.67 15.98 29.63 3. B. alnoides - - - - - - - - - - - - 0.39 1.67 4.32 6.38 4. C. indica - - - - - - - - - - - - 0.39 1.67 0.20 2.26 5. C. tamala 1.42 10.39 0.12 11.93 - - - - - - - - - - - - 6. C. tribuloides - - - - 4.73 3.57 7.91 16.21 48.60 14.81 56.64 120.05 12.79 6.67 20.63 40.09 7. E. acuminata 3.55 5.19 3.02 11.76 6.76 8.93 2.29 17.98 0.28 1.85 0.68 02.81 0.78 1.67 2.68 5.13 8. R. dubia - - - - 6.08 8.93 3.26 18.27 4.19 5.56 4.15 13.90 1.55 3.33 0.19 5.07 9. E. gardneri 0.71 3.90 0.03 4.64 - - - - - - - - - - - - 10. E. japonica - - - - - - - - - - - - 5.82 10.00 0.10 15.92 11. F. floribunda - - - - - - - - - - - - 5.04 8.33 2.36 15.73 12. G. pinata - - - - - - - - 0.28 1.85 0.60 02.73 - - - - 13. G. robusta 2.13 1.30 0.33 3.76 - - - - - - - - - - - - 14. L. nacusua - - - - 18.92 12.50 16.12 47.54 1.96 3.70 0.32 05.98 2.33 1.67 0.53 4.53 15. L. ovalifolia 0.71 2.60 1.02 4.33 6.08 8.93 5.45 20.46 1.40 3.70 0.3 05.40 7.37 5.00 2.14 14.51 16. L. pulcherrima 2.13 3.90 0.16 6.19 - - - - - - - - - - - - 17. M. capitellata 13.48 11.69 4.78 29.95 5.41 5.36 1.65 12.42 14.25 14.81 6.14 35.20 7.37 5.00 1.45 13.82 18. M. esculenta - - - - - - - - 3.07 5.56 2.18 10.81 3.88 6.67 2.06 12.61 19. M. semiserrata 34.75 14.29 5.04 54.08 6.08 12.50 7.61 26.19 1.68 1.85 1.15 04.68 1.16 3.33 0.20 4.69 20. P. cerasoides - - - - - - - - - - - - 5.82 1.67 1.26 8.75 21. P. nepalensis - - - - - - - - - - - - 1.55 1.67 0.87 4.09 22. P. pashia - - - - 16.89 14.29 2.28 33.46 0.28 1.85 1.32 03.45 1.16 5.00 0.61 6.77 23. P. roxburghii - - - - 0.68 1.79 28.91 31.38 3.35 5.56 6.68 15.59 3.10 5.00 19.02 27.12 Banko Janakari, Vol 33 No. 2 17 Dhakal et al. S. N. Name of species Bagdwar Site (BS) Okhreni Site (OS) Sundarijal Site (SS) Panimuhan Site (PS) RD RF RDo IVI RD RF RDo IVI RD RF RDo IVI RD RF RDo IVI 24. Q. lamellosa 4.26 3.90 5.74 13.90 - - - - - - - - 0.78 1.67 0.79 3.24 25. Q. semecarpifolia 24.11 15.58 63.85 103.54 - - - - 2.23 7.41 0.31 09.95 - - - - 26. R. arboreum 12.77 7.79 15.04 35.60 0.68 1.79 0.15 2.62 7.54 11.11 6.40 25.05 2.71 5.00 0.46 8.17 27. H. rhododendrifolium - - - - - - - - 4.47 7.41 0.62 12.50 - - - - 28. S. napaulensis - - - - - - - - - - - - 0.78 1.67 0.35 2.80 29. S. wallichii - - - - 16.22 10.71 17.68 44.61 5.59 9.26 11.32 26.17 27.91 15 23.46 66.37 30. W. fruticosa - - - - - - - - 0.28 1.85 0.11 02.24 - - - - 31. Z. incurva - - - - 1.35 1.79 3.36 6.50 - - - - - - - - DBH of trees The Bagdwar Site possessed the highest number of trees (71) having DBH >50 cm while the Okhreni Site had the least number of such trees (50) (Figure 2). On the other hand, the Sundarijal Site consisted of the highest number of trees (148) with DBH 5-25cm while the Bagdwar Site had the lowest number of such trees (31). Cluster dendrogram A total of 4 plant communities were identified in the SNNP through cluster analysis. Cluster 'A' included all the sample plots from the Panimuhan Site except one (# 33) from the Sundarijal Site. Altogether, 22 species were found in this community having S. wallichii, P. roxburghii, C. indica, and A. nepalensis as the major ones; therefore, this cluster was categorized as 'Schima- Pinus-Alnus community' (Figure 2). Similarly, Cluster 'B' consisted of the sample plots- 13- 21 and 22-32 & 34 from the Okhreni Site, the later ones (plots- 22-32 & 34) mainly consisted of S. wallichii, L. nacusua, and P. pashia, and so it was categorized as 'Schima-Lindera mixed community'. Likewise, Cluster 'C' included all the plots from the Sundarijal Site. The major tree species in this community were S. wallichii, C. tribuloides, M. capitellata, and R. arboreum, and therefore, it was thus categorized as 'Schima- Castanopsis mixed community'. Cluster 'D' had distinctly two sub-clusters- one with the sample plots- 7-12 from the Bagdwar Site dominated by Q. semecarpifolia, R. arborium, and M. semiserrata and another with the sample plots- 1-6 also from the Bagdwar Site with the dominance of Q. semecarpifolia, Myrsine spp., C. tamala and R. arborium, and thus, this cluster was categorized as 'Quercus-Myrsine-Rhododendron mixed community' (Figure 2). Effect of environmental parameters on tree species composition The CCA results showed that the first (CCA1) and second (CCA2) axes accounted for 61% and 35% variations in the species composition (see Figure 3). The tree species like Z. incurva, A. nepalensis and W. fruticosa were closely associated with high tree canopy. Likewise, the shrub species such as Diplomorpha canescens, Maesa chisia and R. arboreum had close relationship with the tree canopy (Figure 3). Similarly, the tree species like Lagerstroemia parviflora, L. pulcherrima and shrubs Rubus ellipticus, and Viburnum cylindricum had optimum association towards the shrub cover, and they showed positive correlation. On the other hand, litter cover also had shown effect on species composition. The species M. semiserrata, Drepanostachyum falcatum, Q. semicarpifolia, Daphne bholua, C. tamala, and Ilex dipyrena have positive correlation with the litter cover while the species such as M. esculenta and Sarcococca coriacea were found to be negatively correlated with the same. The tree species such as M. semiserrata, L. ovalifolia, M. esculenta, and S. coriacea were allied with the rock cover. On the other hand, the species such as Smilex zeylanica, P. parvifolius, and Ageratina adenophora had their optimal abundance towards the herb cover (Figure 3). The PERMANOVA Test showed that the environmental variables (tree canopy, litter cover, and shrub cover) had significant effect on the species composition (p<0.001) whereas the herb cover and rock cover showed no effect on the same. Banko Janakari, Vol 33 No. 2 18 Dhakal et al. Discussion Comparing the richness of tree species among the four study sites in the SNNP, the Panimuhan Site was rich in terms of the number of species followed by the Sundarijal Site. These two sites are located at the entrance point of the national park. At the entrance point, there is an army check post and, therefore, the level of disturbance is low there compared to the other two sites. On the other hand, both the sites are located at more or less the same elevation (1514-1869 m). The Bagdwar and Okhreni sites had a lesser number of species (see Table 1). The Bagdwar Site lies at the top (2795 m) of the national park, and it has matured forest with almost closed canopy due to which the number of species at the understory of tree canopy is lower. Okhreni forest lies at 1945m above the msl within the buffer zone near the Okhreni, Chilauni and Mulpani villages; hence, the forest was used for grazing, collection of fodder and firewood. The low richness of species in this site was due to anthropogenic disturbances. Subedi et al. (2020) also described that the species richness and the abundance decrease with elevation and the disturbances like cutting and grazing are also responsible for decreasing species richness. Santaniello et al. (2016) and Abella & Springer (2015) concluded that partial cutting is beneficial for the growth of plant species because it exposed understory vegetation toward sunlight, which makes growth more vigorously but larger scale has a negative impact on plant diversity. The results of our study are in favor of these studies. The IVI along with the sum of RF, RD and RDo measure how dominant a species is in a given Figure 2: Hierarchical clustered dendrogram showing similarities among different sample plots within the watershed area of SNNP Figure 3: CCA biplot showing the effects of environmental parameters on species composition (complete list of the plant species is presented in Annex I) Banko Janakari, Vol 33 No. 2 19 Dhakal et al. forest area (Curtis & McIntosh, 1950). Based on the IVI, the four study sites within the SNNP (Bagdwar, Panimuhan, Okhreni and Sundarijal) were found to be dominated by different tree species. A dominant species has a significant influence over other organisms in the ecological community. Also, the species tend to have an impact on environmental situations, community diversification, and ecosystem features (Komatsu et al., 2019). The species C. tribuloides at the Sundarijal Site showed the highest density and IVI among the four sites (Table 3), which indicated that this species was the most dominant in this community (C), which is in line with the findings of Sigdel (2008). The lowest densities of E. gardneri and L. ovalifolia at the Bagdwar Site (Table 3) showed that these were the rare species in this community (D). The species- Q. semecarpifolia and S. wallichii at the Bagdwar and Panimuhan sites, respectively, showed the highest frequency indicating the uniformity of distribution of these species in those sites. The species- G. robusta at the Bagdwar Site showed the lowest frequency (1.3, Table 3), which indicated that this species was either irregularly distributed or rare in this community. Presence of high number species indicate the characteristic of more diverse communities. If the species are uniformly distributed, then the diversity index value would be high (Henderson & Southwood, 2016). In our study, all the values were nearer to 1, which indicated that all these sites had moderate diversity (Table 2). The biodiversity indices slightly differed among the sites. The Panimuhan Site had the highest value of Shannon-Weiner Index, indicating high species richness, which might be due to the conservation of the species owing to the army check post nearby this site. On the other hand, the Bagdwar Site had a comparatively low Shannon-Weiner Index, indicating low species richness, which might be due to its location at higher elevation as compared to the other sites. Limbu et al. (2017) also reported that the number of species decreased with the increase in elevation. The observed value of evenness was moderate in this study, which might be due to the apartness of the study sites from one another or due to the differences in their micro-climates. The tree species at the Bagdwar Site consisted of higher DBH (>50 cm) while those at the Sundarijal Site had comparatively lower (<25 cm) girth (Figure 2). The low DBH indicates the mid-level of succession (Bhatt & Khanal, 2010). Poudel et al. (2020), in the Panchase Area of western mid- hills of Nepal, described that higher DBH of trees were found in the forests which were far from anthropogenic disturbance whereas the forests which were easily accessible to humans and are subjected to regular disturbance possessed the trees with low DBH. A total of 4 plant communities were identified in the SNNP through cluster analysis (Figure 2). The cluster 'A' from the Panimuhan Site (south- western aspect) was found to be rich in a number of species with the dominance of S. wallichii, A. nepalensis, and P. roxburghii which was categorized as Schima-Pinus-Alnus Community. The clusters- 'B' and 'C' formed a mixed composition of tree species like S. wallichii, L. nacusua, P. pashia, C. tribuloides, M. capitellata, and R. arboreum towards the Okhreni and Sundarijal sites (eastern aspect), showing the range of distribution of S. wallichii with association of different species towards the eastern and western aspects, and hence this cluster was categorized as 'Schima-Lindera Mixed Community' (Figure 2). Similarly, the presence of R. arboreum at all the sites showed its association with varieties of tree species in all aspects. Cluster 'D' (Quercus- Myrsine-Rhododendron Mixed Community) had a peculiar community at the top of the SNNP with dominancy of Q. semecarpifolia, representing a transitional zone between subtropical and temperate regions (Figure 2). Higher abundance of species such as P. roxburghii at lower elevations, R. arboreum and Q. lanata at mid elevations, and Q. semicarpifolia at higher elevations were also reported by Sigdel (2008). CCA biplot showed the association of species and environmental variables- tree canopy, shrub cover, herb cover, litter cover, and rock cover. The species like Z. incurva, A. nepalensis, W. fruticosa, D. canescens, and M. chisia were found associated with high tree canopy (Figure 3). Z. incurva and A. nepalensis were the trees forming canopy themselves, but the species such as W. Banko Janakari, Vol 33 No. 2 20 Dhakal et al. fruticose, D. canescens, and M. chisia were also found to be forming the canopy as they might be shade-tolerant species as well. The species such as Persea pallida, Drepanostachyum falcatum, M. semiserrata, and Q. semecarpifolia were correlated with litter cover (Figure 3), indicating the species capable of producing high amount of litter. In forest areas, species are subjected to a dense tree canopy that changes light quality & quantity (Holmgren et al. 1997) and water availability which are required to germinate and establish from beneath a thick litter layer (Sydes & Grime 1981). The CCA biplot also showed a group of plant species (mostly shrubs and herbs) towards a high cover of shrubs, herbs, and rock cover areas against high tree canopy (Figure 3). It shows that species such as R. ellipticus, Berberis aristata, Smilex zeylanica, S. coriacea, Osbeckia stellata, L. pulcherrima etc. do not prefer high amounts of litter and shade. Conclusion In the SNNP, four types of plant communities (Schima-Pinus-Alnus Community, Schima- Lindera Mixed Community, Schima-Castanopsis Mixed Community, and Quercus-Myrsine- Rhododendron Community) with 31 tree species representing 19 genera and 18 families were identified. The plant communities were characterized with elevation and aspects. Comparing the richness, the Panimuhan Site was rich in terms of number of tree species. The richness of species was lower at higher elevation (Bagdwar Site) and at the Okhreni Site near the Okhreni Village. The IVI value of C. tribuloides at the Sundarijal Site showed the highest density score and IVI among the four sites. The Panimuhan Site possessed the highest value of diversity indices while the Bagdwar Site had the lower values. On the other hand, the tree species at the Bagdwar Site had higher DBH (>50 cm) while those at the Sundarijal Site had lower DBH<25 cm. E. acuminata, L. ovalifolia, M. capitellata, M. semiserrata, and R. arboreum were found in all the four plant communities. Two species, S. wallichii and R. arboreum showed their association with different species in both the eastern and western aspects. The environmental variables like tree canopy, shrub cover, and litter cover were found to have significant effect on species composition whereas herb cover and rock cover showed no effect on tree species composition in the study sites. Acknowledgments The University Grants Commission, Nepal is acknowledged for providing research grant to the first author (Mr. T. M. Dhakal, Grant No. PhD77/78-S & T 02). Similarly, the authors are thankful to the Department of National Parks and Wildlife Conservation, Nepal and SNNP for providing permission to carry out the study within the park area. Special thanks go to Mr. Nabin Lamichhane for his support in preparing the study site map. Author Contribution Statement TMD: Data collection, analysis, draft writing. LBT: Conception and design, manuscript revision. RKPY: Conception and design, manuscript revision, supervision. CPP: Conception and design, result interpretation, manuscript revision, supervision. 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Berberis aristata Ber.ari S Chutro 29. Morella esculenta Mor.esc T Kaphal 5. B. napaulensis Ber.nap S Jamane Mandro 30. Maesa chisia Mae.chi T Bilaune 6. Betula alnoides Bet.aln T Lek Painyu 31. Osbeckia stellata Osb.ste S Rato Chulesi 7. Caesalpinia decapetala Cae.dec C Areli Kada 32. Phyllanthus parvifolius Phy.par T Khareto 8. Camellia kissi Cam.kis S Chiyaapaate 33. Pinus roxburghii Pin.rox T Rani Salla 9. Castanopsis indica Cas.ind T Dhale Katus 34. Prunus cerasoides Pru.cer T Painyu 10. C. tribuloides Cas.tri T Musure Katus 35. P. nepalensis Pru.nep T - 11. Cinnamomum tamala Cin.tam T Tejpat 36. Pyrus pashia Pyr.pas T Mayal 12. Daphne bholua Dap.bho S Lokta 37. Quercus lamellosa Que.lam T Falant 13. Diplomorpha canescens Dip.can S Phurke Paat 38. Q. semecarpifolia Que.sem T Kharsu 14. Drepanostachyum falcatum Dre.fal S Nigalo 39. Rhaphiolepis dubia Rha.dub T Jure Kafal 15. Edgeworthia gardneri Edg.gar T Argeli 40. Rhododendron arboreum Rho.arb T Gurans 16. Eurya acuminata Eur.acu T Saano Jhingane 41. Rubus ellipticus Rub.ell S Ainselu 17. E. japonica Eur.jap T Jhingane 42. Smilax zeylanica Smi.zey C Kukur Daaino 18. Garuga pinnata Gar.pin T Dabdabe 43. Sarcococca coriacea Sar.cor S Telpaaro 19. Gaultheria fragrantissima Gau.fra S Dhasingre 44. Saurauia napaulensis Sau.nap T Gogan 20. Grevillea robusta Gre.rob T Kaenyo 45. Schima wallichii Sch.wal T Chilaune 21. Heptapleurum rhododendrifolium Hep.rho T - 46. Smilax aspera Smi.asp C Kukur Daaino 22. Ilex dipyrena Ile.dip S Seto Khasru 47. Viburnum cylindricum Vib.cyl S Ghode Khari 23. Lindera pulcherrima Lin.pul T Phusre 48. Woodfordia fruticosa Woo.fru T Dhairo 24. L. nacusua Lin.nac T - 49. Ziziphus incurva Ziz.inc T Hade Bayar 25. Lyonia ovalifolia Lyo.ova T Angeri Note: C = Climber; H = Herb; S = Shrub; and T = Tree. _Hlk154127214 _Hlk152447776 _Hlk152692305 _heading=h.30j0zll