REINWARDTIA Vol. 22. No. 1. pp: 37‒53 DOI: 10.55981/reinwardtia.2023.4565 37 FLORISTIC COMPOSITION AND STRUCTURE OF VEGETATION IN GUNUNG SALAK GEOTHERMAL POWER PLANT, WEST JAVA, INDONESIA Received March 28, 2023; accepted May 25, 2023 AFRI IRAWAN PT Aksioma Amerta Bumi, Jln. Seruni No. 25, Loji, Bogor 16117, Indonesia. Email: afri.irawan31@gmail.com. https://orcid.org/0000-0002-1013-0613. PENIWIDIYANTI Research Center for Ecology and Ethnobiology, National Research and Innovation Agency (BRIN), Jln. Raya Jakarta- Bogor Km. 46, Cibinong, Bogor 16911, Indonesia. Email: niwidiyan@gmail.com. https://orcid.org/0000-0003-4019-165X. AINURROFIAH Yayasan Botani Tropika Indonesia, Jl. Seruni No. 25, Loji, Bogor 16117, Indonesia. Email: a.ainurrofiah@gmail.com. https://orcid.org/0009-0009-4561-5504. HERI DESTRIANTO Yayasan Botani Tropika Indonesia, Jl. Seruni No. 25, Loji, Bogor 16117, Indonesia. Email: heri.des3@gmail.com. https://orcid.org/0009-0006-3858-1957. MULYADI KUSUMAH PT PLN Indonesia Power Unit PLTP Gunung Salak, Pamijahan, Bogor 16810, Indonesia. Email: mulyadi.kusumah@plnindonesiapower.co.id. VICKY APRIANDANA PT PLN Indonesia Power Unit PLTP Gunung Salak, Pamijahan, Bogor 16810, Indonesia. Email: vicky.apriandana@plnindonesiapower.co.id. ABSTRACT IRAWAN, A., PENIWIDIYANTI, AINURROFIAH, DESTRIANTO, H., KUSUMAH, M. & APRIANDANA, V. 2023. Floristic composition and structure of vegetation in Gunung Salak geothermal power plant, West Java, Indonesia. Reinwardtia 22(1): 37‒53. — This research had been conducted in the forest area around the Gunung Sa- lak Geothermal Power Plant of PT. PLN Indonesia Power. Plant diversity data in the geothermal power plant area had yet to be fully available. This study aimed to analyze the composition and structure of vegetation in the conservation forest area around the Gunung Salak Geothermal Power Plant unit. This study used a quadrat plot with a purposive sampling method. We sampled 873 individuals from 56 families of 110 species, consisting of native and introduced species. Some introduced flora species that have the potential to become invasive include Calliandra houstoniana, Asystasia gangetica, Bellucia pentamera, Miconia crenata, Maesopsis eminii, and Solanum torvum. The families with the highest number of species at each growth level were Fagaceae (tree), Fagaceae (pole), Arecaceae and Moraceae (sapling), also Acanthaceae, Arecaceae, Melastomataceae, and Poaceae in the understory. Several species of plant at the site are listed as Endangered (EN) based on the IUCN Red List, including A lpinia scabra, Castanopsis argentea, and Dipterocarpus hasseltii. These endangered plants are expected to become priority for conservation strategies and action plans. The Important Value Index (IVI) analysis shows different values at each growth stage. The highest IVI at the seedling and herb was Selaginella plana (29.74), the sapling was Macaranga triloba (20.59), the pole was Ficus fistulosa (43.27), and the tree was Schima wallichii (54.90). The value of the Shannon-Wiener (H') diversity index was 3.784, which indicates that the level of diversity is high. Key words: Conservation, Dipterocarpus hasseltii, endangered, Halimun-Salak, Importance Value Index. ABSTRAK IRAWAN, A., PENIWIDIYANTI, AINURROFIAH, DESTRIANTO, H., KUSUMAH, M. & APRIANDANA, V. 2023. Komposisi dan struktur vegetasi di pembangkit listrik tenaga panas bumi Gunung Salak, Jawa Barat, Indonesia. Reinwardtia 22(1): 37‒53. — Penelitian ini telah dilaksanakan di kawasan hutan di sekitar Pembangkit Listrik Tenaga Panas Bumi (PLTP) Gunung Salak, PT. PLN Indonesia Power. Data keanekaragaman tumbuhan di daerah pembangkit listrik tenaga panas bumi belum sepenuhnya tersedia. Penelitian ini bertujuan untuk menganalisis komposisi dan struktur vegetasi kawasan hutan konservasi di sekitar unit PLTP - Gunung Salak. Penelitian ini menggunakan kuadrat plot dengan metode purposive sampling. Sampel individu tumbuhan terkumpul sebanyak 873 yang termasuk ke dalam 56 suku dari 110 jenis. Jenis flora tersebut terdiri dari jenis asli dan jenis asing. Beberapa jenis tumbuhan asing yang berpotensi menjadi invasif adalah Calliandra houstoniana, A systasia gangetica, Bellucia pentamera, Miconia crenata, Maesopsis eminii, dan Solanum torvum. Suku tumbuhan dengan jumlah jenis terbanyak pada tiap tingkat pertum- buhan yaitu; Fagaceae (pohon), Fagaceae (tiang), Arecaceae dan Moraceae (pancang), serta Acanthaceae, Arecaceae, Melastomataceae, dan Poaceae pada tumbuhan bawah. Beberapa jenis tumbuhan di lokasi tersebut berstatus Endan- mailto:afri.irawan31@gmail.com mailto:niwidiyan@gmail.com mailto:a.ainurrofiah@gmail.com mailto:niwidiyan@gmail.com mailto:vicky.apriandana@plnindonesiapower.co.id https://dx.doi.org/10.55981/reinwardtia.v22i1.4565 https://orcid.org/0000-0002-1013-0613 https://orcid.org/0000-0003-4019-165X https://orcid.org/0009-0009-4561-5504 https://orcid.org/0009-0006-3858-1957 REINWARDTIA 38 [VOL.22 INTRODUCTION Gunung Halimun Salak National Park (GHSNP) is the largest tropical mountain rainfor- est conservation area on Java Island, with more than 700 species of plants that can be found (Prasetio et al., 2022). It is divided into several zone classifications, including utilization zones within conservation areas with natural potential that can be utilized for tourism purposes and utili- zation of other environmental services (Ministry of Forestry Regulation No. 56 of 2006). Now, one of the geothermal potentials around Mount Salak has been utilized and managed by PT PLN Indo- nesia Power since 1994 under the Geothermal En- vironmental Services Management Permit (Izin Pemanfaatan Jasa Lingkungan Panas Bumi (IPJLPB)) that has been issued. Various conserva- tion activities, such as planting and maintaining conservation areas and monitoring biodiversity have been carried out for corporate social respon- sibility for the sustainability of forest ecosystems around the geothermal power plant unit (Peniwi- diyanti et al., 2021). The condition of the moun- tain rainforest ecosystem around the Gunung Sa- lak Geothermal Power Plant unit must be ma- naged to remain the best and most sustainable. Basic studies regarding the condition of the cover area around geothermal in Indonesia are generally carried out as a preliminary study before exploring the source location of the power plant. The methods commonly used are based on remote sensings, such as Enhanced Vegetation Index (EVI) using Landsat 8 imagery in the Ungaran Mount geothermal area (Nugroho & Domiri, 2015) or identifying using the Normalized Differ- ence Vegetation Index (NDVI) method in Lam- pung (Immanuel et al., 2019). Whereas in the Gunung Salak Geothermal Power Plant unit, the biodiversity studies that have been published in- clude the diversity of bird species and herpetofau- na particularly (Husodo et al., 2020; Megantara et al., 2022). Studies on detailed plant diversity for the forest area around the geothermal area have yet to be available and published in Indonesia. Whereas research on the diversity of the composi- tion and structure of plants around geothermal areas is very important as basic information for evaluating conservation area management and as an indicator of the health of mountain rainforest ecosystems. So, this research needs to collect in- formation about the diversity of plant species around the geothermal area. This study aimed to analyze the composition and structure of the vege- tation in the conservation forest area around the Gunung Salak Geothermal Power Plant unit. MATERIALS AND METHODS Study Area The research was conducted from April to May 2022 in the Gunung Salak Geothermal Plant con- servation forest at PT. PLN Indonesia Power. The coordinates position 6 o 44'25.6” S and 106 o 38'35.6” E (Fig. 1). PT. PLN Indonesia Power has genera- tion units and services in Kamojang and Gunung Salak. The Gunung Salak power plant unit is inside the conservation area of the Gunung Halimun Sa- lak National Park (GHSNP). Observations were made at 960–1,028 m asl with an air temperature of 23–32°C, humidity of 23–32%, and soil pH 6.2– 7.5. The topography of the research site is slightly flat and uphill, covering an area that are slightly open to densely covered by vegetation. The research was conducted on the Eastern and Western sides of the geothermal unit (Fig. 1). The whole forest area can originally be defined as a primary forest. However, the forested area was affected by the geothermal power plant develop- ment. The Eastern and Western forests have slight- ly different contours and are separated mostly by infrastructure, such as office buildings, roads, brid- ges, power plants, cooling towers, and steam pipe- lines. A rocky stream crosses the eastern forest. The contours of the Eastern forest are ridges, val- leys, and cliffs. The Western forest has a larger area than the Eastern side and is bordered by ri- vers. In this forest, the land condition at some points is low slopes, ridges, and valleys with cliffs at some points that are difficult to access. The company introduced a replanting program in sever- al cleared areas to maintain the forested area, as shown in Fig. 1. The replanting program was con- ducted from 2017 to 2021; every planted individu- al was labeled (Peniwidiyanti et al., 2021) and monitored. Thus, planted individuals and naturally regenerated individuals can be easily distinguished. The species used for replanting were Schima wal- gered (EN) berdasarkan IUCN Redlist, antara lain Alpinia scabra, Castanopsis argentea, dan Dipterocarpus has- seltii. Tumbuhan yang terancam punah ini diharapkan menjadi jenis tumbuhan prioritas untuk strategi dan rencana aksi konservasi. Analisis indeks nilai penting (INP) menunjukkan nilai yang berbeda pada setiap tahap pertumbuhan. Nilai INP tertinggi pada semai dan herba yaitu Selaginella plana (29,74), pancang yaitu Macaranga triloba (20,59), tiang yaitu Ficus fistulosa (43,27), dan pohon yaitu Schima wallichii (54,90). Nilai indeks keanekaragaman Shannon- Wiener (H') sebesar 3,784, yang menunjukkan bahwa tingkat keanekaragamannya tinggi. Kata kunci: Dipterocarpus hasseltii, genting, Halimun-Salak, Indeks Nilai Penting, konservasi. IRAWAN et al.: Floristic composition and structure of vegetation in geothermal power plant, West Java. 2023] 39 lichii, Liquidambar excelsa, Litsea spp., Syzygium lineatum, and Castanopsis argentea. Data Collection Vegetation data were collected using a quadratic plot method (Mueller-Dombois & Ellenberg, 1974). Fifteen (15) plots were made, 11 on the western and four on the eastern side. Three (3) of the western side plots were located in the replant- ing areas. The coordinate of all plot’s location was then recorded. The observation plot size was 20 m × 20 m and located by using purposive sampling methods. Each plot was divided into four sub-plots to measure vegetation based on growth stages. Ob- servation plot measuring 20 m × 20 m for tree, 10 m × 10 m for pole, 5 m × 5 m for sapling and shrub, and 2 m × 2 m for understory as seedling and herb. Each plant in the plot was recorded for the species name, the number of individuals, and stem diameter at breast height (DBH) using a di- ameter tape, then as a sapling or tree. For identifi- cation purposes, we collected leaves, twigs, fruit, and flower of the plant in the plots, photographed each directly in the field for each specimen and made some herbarium. Species identification is needed to know the sci- entific names of plant species. The following refe- rences were used in the species identification pro- cess referring to the Mountain Flora of Java (van Steenis, 1971), A Picture Guide of Forest Trees in Gunung Gede Pangrango National Park, Indonesia (Toyama et al., 2018), Flora of Java (Backer & van den Brink Jr, 1963; Backer & van den Brink Jr, 1965; Backer & van den Brink Jr, 1968), and Plant of Southeast Asia (Slik, 2009). Validation of scientific species names and distribution refers to Plant of the World Online (POWO, 2022). Distribution status is categorized as either na- tive or introduced species. Native plant species occur naturally in a specific region without human intervention or other region’s introduction. Intro- duced plant species, also known as non-native plant species, are intentionally or unintentionally brought into a region or ecosystem from another region. Determination of native or introduced plant species refers to Plant of the World Online (POWO, 2022), Global Invasive Species Database (GISD, 2023), and Central for Agricultural and Bioscience International (CABI, 2022). The plant species that have been identified are also known for their conservation status. The conservation status was analyzed based on data from the The International Union for Conservation of Nature (IUCN) Red List, Regulation of the Minister of Fig. 1. Study area on Gunung Salak Geothermal Plant at PT. PLN Indonesia Power. REINWARDTIA 40 [VOL.22 Environment and Forestry No.106/2018 Regula- tion, and the Convention on International Trade in Endangered Species (CITES). Data Analysis Importance value index (IVI) The ecological parameters were analyzed by the Importance Value Index (IVI). The IVI helped to know about significance of species in the com- munity structure. The Importance Value Index can be calculated using the following formula (Phillips, 1959; Mueller-Dombois & Ellenberg, 1974): Density (D) = number of individual species A/ sample plot area Relative density (RD) = (number of individual species A/number of all individual spe- cies) × 100% Frequency (F) = number of the plot with spe- cies A/total number of all plot Relative frequency (RF) = (frequency of spe- cies A/total frequency of all species) × 100% Dominance (Do) = basal area of species A/ sample plot area Relative dominance (RDo) = (dominance of species A/total dominance of all species) × 100% Sapling and understory calculation is IVI=RD+FR, while calculated for pole and tree is IVI=RD+RF+RDo. Species diversity, richness, evenness, and domi- nance The diversity of plant was determined using the Shannon-Wiener diversity index (Michael, 1984; Magurran, 1988) as the following formula: where Where, pi is the proportion of individuals found in the i th species, ni is the number of individuals of the i species, and N is the total number of indivi- duals of all species. The diversity index shows the amount of species diversity in a habitat study. The value scale of this index is H' < 1.5, indicating that the diversity obtained is low, the value of H' 1.5–3.5 indicates that the diversity obtained is moderate, and the value of H' > 3.5 indicates that the diversity is high (Wilhm & Dorris, 1968). Species richness was calculate using the Mar- gallef Index (Magurran, 1988) as the following formula: Dmg = (S-1)/ln N Where, Dmg is the richness index of community A, S is the total number of species, and ln N is a natural logatithmic value of the total number of individuals. Species richness index is classified as high (Dmg > 5), moderate (3.5 ≤ Dmg ≤5), and low (Dmg < 3.5). Species evenness measures the relative abun- dance of the different species in an area. Species evenness was calculated using the following for- mula (Ludwig & Reynolds, 1988): Where, E is the evenness index of community A, H’ is the Shannon-Wiener diversity index, and ln S is a natural logarithmic value of the total number of species. The last quantitative analysis is the domi- nance index using the following formula (Odum, 1971): Where, C is the dominance index, ni is the number of individuals of the i species, and N is the total number of individuals of all species. RESULTS Floristic composition In this study, plant species in the Gunung Salak Power Plant unit recorded 873 individuals from 110 species in 56 families (Table 1), of which 58 species of them are trees, 15 shrubs, 17 herbs, five lianas, six palms, and nine fern species. The tree species that can be found were puspa (Schima wal- lichii), rasamala (Liquidambar excelsa), pasang (Lithocarpus spp.), saninten (Castanopsis ar- gentea), and ki hujan (Engelhardia spicata). Pa- lahlar/keruing (Dipterocarpus hasseltii) had very few populations in this forest. The vegetation composition of Gunung Salak Geothermal Power Plant areas mostly consisted of native plant species. However, there were few in- troduced plant species (Table 1). Introduced spe- cies found in this research means plant species imported from other areas into a native plant com- munity and can cause environmental damage due to their increasing population (Tjitrosoedirdjo et al., 2016). These plants include Calliandra housto- niana, Asystasia gangetica, Bellucia pentamera, Miconia crenata, Maesopsis eminii, and Solanum torvum. Among those species, the most abundant populations at the study site were C. houstoniana and M. eminii. IRAWAN et al.: Floristic composition and structure of vegetation in geothermal power plant, West Java. 2023] 41 No Species Local name Habitus Distribution status Acanthaceae 1 Asystasia gangetica (L.) T.Anderson Jukut Israel Herb Introduced 2 Barleria cristata L. Landep Shrub Native 3 Strobilanthes filiformis Blume Bubukuan Shrub Native Actinidiaceae 4 Saurauia pendula Blume Ki Leho Tree Native Altingiaceae 5 Liquidambar excelsa (Noronha) Oken Rasamala Tree Native Anacardiaceae 6 Mangifera cf. laurina Blume Limus Piit Tree Native Annonaceae 7 Huberantha rumphii (Blume ex Hensch.) Chaowasku Wihu Tree Native 8 Goniothalamus macrophyllus (Blume) Zoll. Empalis Tree Native 9 Monoon lateriflorum (Blume) Miq. Jalatrung Tree Native Araceae 10 Apoballis rupestris (Zoll. & Moritzi) S.Y.Wong & P.C.Boyce Taleus Herb Native 11 Arisaema filiforme (Reinw.) Blume Ki Acung Herb Native Araliaceae 12 Macropanax concinnus Miq. (2) Pangpung Tree Native Arecaceae 13 Calamus javensis Blume Rotan Palm Native 14 Calamus reinwardtii Mart. Rotan Palm Native 15 Caryota mitis Lour. Sarai Palm Native 16 Pinanga coronata (Blume ex Mart.) Blume Bingbin Palm Native 17 Pinanga javana Blume Hanyawar Palm Native 18 Plectocomia elongata Mart. Ex Blume Rotan Badak Palm Native Asparagaceae 19 Dracaena sp. Ki Beusi Shrub Native Aspleniaceae 20 Asplenium nidus L. Paku Sarang Bu- rung Fern Native Asteraceae 21 Strobocalyx arborea (Buch.-Ham.) Sch.Bip. Merambung Tree Native Begoniaceae 22 Begonia isoptera Dryand. ex Sm. Begonia Herb Native 23 Begonia muricata Blume Begonia Herb Native Cyatheaceae 24 Sphaeropteris glauca (Blume) R.M.Tryon (*) Paku Tiang Fern Native Cyperaceae 25 Scleria ciliaris Nees Jukut Ilat Herb Native Table 1. Plant diversity in Gunung Salak Geothermal Power Plant unit REINWARDTIA 42 [VOL.22 Dilleniaceae 26 Dillenia obovata (Blume) Hoogland Ki Sempur Tree Native Dipterocarpaceae 27 Dipterocarpus hasseltii Blume (1) Palahlar/Keruing Tree Native Elaeocarpaceae 28 Elaeocarpus petiolatus (Jack) Wall. Ganitri Gunung Tree Native 29 Sloanea sigun (Blume) K.Schum. Beleketebe Tree Native Euphorbiaceae 30 Homalanthus populneus (Geiseler) Pax Kareumbi Tree Native 31 Macaranga denticulata (Blume) Müll.Arg. Mara Tree Native 32 Macaranga tanarius (L.) Müll.Arg. Mara Tree Native 33 Macaranga triloba (Thunb.) Müll.Arg. Mara Tree Native 34 Mallotus paniculatus (Lam.) Müll.Arg. Calik Angin Tree Native Fabaceae 35 Abrus precatorius L. Saga Rambat Liana Introduced 36 Calliandra houstoniana (Mill.) Standl. Kaliandra Beureum Tree Introduced Fagaceae 37 Castanopsis argentea (Blume) A.DC. (1)(a) Saninten Tree Native 38 Castanopsis javanica (Blume) A.DC. Ki Hiur Tree Native 39 Lithocarpus elegans (Blume) Hatus. ex Soepadmo Pasang Tree Native 40 Lithocarpus indutus (Blume) Rehder (2) Pasang Tree Native 41 Lithocarpus sundaicus (Blume) Rehder Pasang Tree Native 42 Quercus lineata Blume Pasang Tree Native Gesneriaceae 43 Cyrtandra grandis Blume Reungdeu Herb Native 44 Cyrtandra picta Blume Ramokuya Herb Native Hydrangeaceae 45 Hydrangea febrifuga (Lour.) Y.De Smet & Granados Kaciput Shrub Native Hypoxidaceae 46 Curculigo capitulata (Lour.) Kuntze Congkok/marasi Herb Native Juglandaceae 47 Engelhardia spicata Lechen ex Blume Ki Hujan Tree Native Lauraceae 48 Beilschmiedia madang (Blume) Blume Huru Madang Tree Native 49 Cinnamomum parthenoxylon (Jack) Meisn. Selasihan Tree Native 50 Litsea diversifolia Blume Madang Tree Native 51 Machilus rimosa Blume Ki Puket Tree Native 52 Neolitsea javanica (Blume) Backer Huru Batu Tree Native Magnoliaceae 53 Magnolia sumatrana (Miq.) Figlar & Noot. Manglid Tree Native Malvaceae 54 Commersonia bartramia (L.) Merr. Andilau Tree Native 55 Sterculia oblongata R.Br. Hantap Tree Native IRAWAN et al.: Floristic composition and structure of vegetation in geothermal power plant, West Java. 2023] 43 Marantaceae 56 Phrynium sp. Habana Herb Native Melastomataceae 57 Bellucia pentamera Naudin Tangkalak Tree Introduced 58 Dissochaeta gracilis Blume Harendong Areuy Liana Native 59 Melastoma malabathricum L. Harendong Jawa Shrub Native 60 Memecylon oleifolium Blume Ki Beusi Tree Native 61 Miconia crenata (Vahl) Michelang. Harendong Bulu Shrub Introduced 62 Pternandra azurea (Blume) Burkill Tree Native Meliaceae 63 Epicharis densiflora Blume Ki Panongo Tree Native Moraceae 64 Artocarpus elasticus Reinw. ex Blume Teureup Tree Native 65 Ficus fistulosa Reinw. ex Blume Kondang Tree Native 66 Ficus glaberrima Blume Ara Tree Native 67 Ficus padana Burm.f. Hamerang Badag Tree Native 68 Ficus tricolor Miq. Hemerang Tree Native 69 Ficus variegata Blume Kondang Tree Native Myristicaceae 70 Knema cinerea (Poir.) Warb. Darah-darah Tree Native Myrtaceae 71 Syzygium antisepticum (Blume) Merr. & L.M.Perry Ki Tambaga Tree Native 72 Syzygium cerasiforme (Blume) Merr. & L.M.Perry Ki Sireum Tree Native Nephrolepidaceae 73 Nephrolepis biserrata (Sw.) Schott Paku Pedang Fern Native Oleaceae 74 Chionanthus ramiflorus Roxb. Ki Bokol Tree Native Orchidaceae 75 Appendicula sp. Anggrek Herb Native 76 Calanthe speciosa (Blume) Lindl. Anggrek Herb Native Pandanaceae 77 Freycinetia sp. Pandan Areuy Liana Native Pentaphylacaceae 78 Eurya acuminata DC. Ki Menir Tree Native Phyllanthaceae 79 Antidesma montanum Blume Ki Huut Tree Native 80 Glochidion zeylanicum (Gaertn.) A.Juss. Semutan Tree Native Poaceae 81 Dinochloa scandens (Blume ex Nees) Kuntze Awi Cangkoreh Shrub Native 82 Oplismenus burmanni (Retz.) P.Beauv. Jukut Bulu Herb Native 83 Setaria latifolia (Scribn.) R.A.W.Herrm. Jukut Kerpe Herb Introduced Polypodiaceae 84 Microsorum sp. Paku Fern Native REINWARDTIA 44 [VOL.22 85 Polypodium sp. Paku Daun Fern Introduced Pteridaceae 86 Hemionitis sp. Paku Fern Native 87 Pteris sp. Paku Fern Native Rhamnaceae 88 Maesopsis eminii Engl. Kayu Afrika Tree Introduced Rosaceae 89 Rubus moluccanus L. Arben Shrub Native Rubiaceae 90 Chassalia curviflora (Wall.) Thwaites Ki Kopi Shrub Native 91 Eumachia montana (Blume) I.M.Turner Soka Gunung Shrub Native 92 Lasianthus stipularis Blume Kokopian Shrub Native 93 Pavetta montana Reinw. ex Blume Angsoka Shrub Native 94 Psychotria divergens Blume Soka Gunung Shrub Native Rutaceae 95 Melicope latifolia (DC.) T.G.Hartley Ki Sampang Tree Native 96 Melicope lunu-ankenda (Gaertn.) T.G.Hartley Ki Sampang Tree Native Salicaceae 97 Flacourtia rukam Zoll. & Moritzi Rukem Tree Native Selaginellaceae 98 Selaginella plana (Desv.) Hieron. Paku Rane Fern Native Smilacaceae 99 Smilax zeylanica L. Bungkus Tree Native Solanaceae 100 Solanum torvum Sw. Takokak Shrub Introduced Staphyleaceae 101 Dalrympelea sphaerocarpa (Hassk.) Nor-Ezzaw. Ki Bancet Tree Native Tectariaceae 102 Tectaria sp. Paku Takta Fern Native Theaceae 103 Schima wallichii (DC.) Korth. Puspa Tree Native Urticaceae 104 Dendrocnide stimulans (L.f.) Chew Pulus Tree Native 105 Elatostema strigosum Hassk. Katilapro Herb Native 106 Oreocnide rubescens (Blume) Miq. Nangsi Tree Native 107 Poikilospermum suaveolens (Blume) Merr. Mentawan Liana Native Vitaceae 108 Leea indica (Burm.f.) Merr. Girang Shrub Native Zingiberaceae 109 Alpinia scabra (Blume) Náves (1) Bangle Herb Native 110 Etlingera coccinea (Blume) S.Sakai & Nagam. Tepus Herb Native Notes: (1) Endangered (EN-IUCN); (2) Vulnerable (VU-IUCN); (a) Protected (P.106/2018); (*) Appendix II (CITES). IRAWAN et al.: Floristic composition and structure of vegetation in geothermal power plant, West Java. 2023] 45 The families with the highest number of species were Arecaceae, Fagaceae, Melastomataceae, and Moraceae, each consisting of six species (Fig. 2). In contrast, the lowest number of species was only one species in the following families: Actinidiace- ae, Altingiaceae, Anacardiaceae, Araliaceae, As- paragaceae, Aspleniaceae, Asteraceae, Cyathea- ceae, Cyperaceae, Dilleniaceae, Dipterocarpaceae, Hydrangeaceae, Hypoxidaceae, Juglandaceae, Magnoliaceae, Marantaceae, Meliaceae, Myristi- caceae, Nephrolepidaceae, Oleaceae, Pandanace- ae, Pentaphylacaceae, Rhamnaceae, Rosaceae, Salicaceae, Selaginellaceae, Smilacaceae, Sola- naceae, Staphyleaceae, Tectariaceae, Theaceae, and Vitaceae. The number of families and species compared at each growth level. The growth stages are tree, pole, sapling, and understory (seedling and herb). The data shows that at each growth stage, there are differences in the number of families and species (Fig. 3). The highest were understory plants (36 families and 53 species) and the lowest number of families and species were in pole stage (22 fami- lies and 32 species). Fagaceae dominated plant species at the tree level and consist of five species. Fagaceae dominated the pole level and consists of four species. The sapling level was dominated by Arecaceae and Moraceae, each consisting of four species. In contrast, the understory was dominated by Acanthaceae, Arecaceae, Melastomataceae, and Poaceae, each consisting of three species. Rare and endangered species were explained based on their conservation status (Table 1). Six species are included in the criteria for rare and endangered species that grow around the Gunung Salak Geothermal Power Plant unit. These species in the Endangered category (EN-IUCN) were Alpinia scabra (bangle), Castanopsis argentea (saninten), and Dipterocarpus hasseltii (palahlar/ keruing). Castanopsis argentea is also a protected species by the government of Indonesia through regulations from the Ministry of Environment and Forestry. One fern species in the CITES appendix is Sphaeropteris glauca (App II). Fig. 4 shows palahlar, one of the endangered tree species. Structure of vegetation The vegetation structure at Gunung Salak Geo- thermal Power Plant is shown in Fig. 5. The graph of individual density at each growth stage and the number of individuals in several diameter classes show an inverted J-shaped curve. The inverted J curve shows that the forest condition around the power plant is still balanced, and the regeneration process runs well at all growth stages. Some species dominate the number of the individual at each growth stage. Schima wallichii (puspa) has the highest number of individuals with 23 individuals, followed by Ficus padana (hamerang badag) with 14 individuals. Schima wallichii is common in the Java mountains (van Steenis, 1971). At the pole stage, the species with the highest number of individuals were Ficus fistulosa (beunying) with 15 individuals, and Eurya acuminata (ki menir) with 11 individuals. The species most commonly recorded at sapling were Calliandra houstoniana (kaliandra beureum) with 12 individuals and Macaranga triloba (mara) with eight individuals. The understory was Sela- ginella plana (paku rane) with 115 individuals and Barleria cristata (landep) with 70 individuals. Selaginella plana, has a habitus as ferns with a wide distribution, in the lowlands and mountain forests (Rahmad & Akomolafe, 2018; Setyawan et al., 2018; Coritico & Amoroso, 2020). Trees with a more than 75 cm diameter around the Gunung Salak Geothermal Power Plant unit recorded as many as six individuals (Fig. 5B) of four species. The trees with the three largest diameters were the Schima wallichii (116 cm), followed by Magnolia sumatrana (97 cm) and S. wallichii (92 cm). Importance Value Index (IVI) and diversity index Plants with the highest Important Value Index (IVI) showed that these species have the most sig- nificant influence on a forest ecosystem and can control them through the dominance of their den- sity and abundance. Table 2 shows the five plant species with the highest IVI at each growth stage. Based on the IVI analysis, seedling and herb were dominated by S. plana (29.74) and Miconia crena- ta (20.84). At the sapling, the dominant species were Macaranga triloba (20.59) and Calliandra houstoniana (17.18). At the pole, the high IVI were Ficus fistulosa (43.27), Eurya acuminata (36.91), and S. wallichii (33.35). At the tree, the high IVI was S. wallichii (54.90), Maesopsis emi- nii (30.27), and Ficus padana (22.04). Analysis of Shannon-Wiener diversity index, species richness index, evenness index, and domi- nance index value calculated by total data. Analy- sis of the Shannon-Wiener diversity index (H') is 3.784. Based on the index value category H', the diversity of flora around Gunung Salak Geother- mal Power Plant is classified as high diversity. The species richness index is 16.391, which indi- cates that the species are in the high category. The species evenness index is 0.802, and the domi- nance index value is low as 0.042. DISCUSSION The forest ecosystem around the power plant can be considered the lower mountain forest of Java due to its plant diversity characteristics. The forest ecosystem is overgrown by natural trees typical of the flora of the Java Mountains. Cas- tanopsis argentea, Schima wallichii, Sloanea sigun, Lithocarpus spp., Quercus lineata, and REINWARDTIA 46 [VOL.22 Fig. 2. Floristic composition of the study area. Fig. 3. Number of families and species at each growth stage. Fig. 4. Palahlar/Keruing (Dipterocarpus hasseltii). Photos by Afri Irawan IRAWAN et al.: Floristic composition and structure of vegetation in geothermal power plant, West Java. 2023] 47 Engelhardia spicata are common species found in the mountainous regions of Java (Backer & van den Brink Jr, 1963; Backer & van den Brink Jr, 1965; Backer & van den Brink Jr, 1968; van Steenis, 1971; Toyama et al., 2018). Some introduced plant species can become In- vasive Alien Plant Species (IAPS). If not handled properly, IAPS can defeat the native flora (Tjitro- soedirdjo et al., 2016). Introduced plant species that were found and had potential as IAPS include Calliandra houstoniana, Asystasia gangetica, Bel- lucia pentamera, Miconia crenata, Maesopsis eminii, and Solanum torvum. Invasive alien plant species found in abundant populations at the study site were C. houstoniana and M. eminii. Callian- dra houstoniana native to Central America. Des- pite the ability of this species to fixing nitrogen (Izerimana & Hirwa, 2019) that was important for the forest community, Calliandra has been report- ed to have a rapid growth rate and high densities that will increase its invasiveness (Yudaputra, 2020). While, M. eminii, an African exotic spe- cies, has been reported as fast-growing species and disturbed forest indicator in Bodogol forest, Gunung Gede Pangrango National Park (Helmi et al., 2009). Maesopsis eminii seeds are dispersed by birds and primates, thus accelerating their dis- tribution (Sambas et al., 2018). Based on conservation status analysis, some plant species are categorized as rare, threatened, and endangered (RTE) species. These species listed in the Endangered category (EN-IUCN) were A lpinia scabra (bangle), Castanopsis argen- tea (saninten), and Dipterocarpus hasseltii (palahlar/keruing). Castanopsis argentea is also a protected species based on the Minister of Environment and Forestry Regulation No. 106 of 2018. Castanopsis argentea is a species listed in the 2019-2029 national priority tree conservation strategy (Hamidi et al., 2019). Other species in the Vulnerable category (VU-IUCN) were Lithocarpus indutus (Pasang) and Macropanax concinnus (Pangpung). The species is not protected, but is included in the Appendix 2 category of CITES, Sphaeropteris glauca (paku tiang) from the Cyatheaceae. Sphaeropteris glauca trades as an ornamental plant. Without regulation in its exploitation, this species will become extinct. All important plants species are native to Java and the western part of Malesia. Castanopsis argentea, Dipterocarpus hasseltii, Lithocarpus indutus, and Macropanax concinnus are rare tree species according to the IUCN red list. Cas- tanopsis argentea was found in only four stands in the study plots. Castanopsis argentea can grow on arable land and dry, and rocky soils, but its popu- lation will decrease at higher elevations (Hilwan & Irfani, 2018). These stands grow in sloping are- as. Dipterocarpus hasseltii and L. indutus grew in the forest on the west side of the power plant. Dipterocarpus hasseltii is found naturally in lowland areas in Sumatra and Kalimantan (Ashton, 1982) but rarely in the Java mountains. Apart from Mount Salak, D. hasseltii remains on Mount Halimun (Uji, 2002; Yusuf, 2004). Dipterocarpus hasseltii was also located in the Situ Gunung, Gunung Gede Pangrango National Park, but in subsequent studies, it was not found anymore at that location (Kalima & Wardani, 2013). In lowland forest at West Java, D. hasseltii is found in Leuweung Sancang Nature Reserve, Garut (Sidiyasa et al., 1985; Wardani et al., 1988; Kalima et al., 1988; Usmadi, 2015) and Yanlapa Nature Reserve, Bogor (Wardani, 2011). In rela- tively large numbers, Macropanax concinnus was found in the power plant forest area in relatively large number (± 20 ind/ha). This tree species is a high-density species in the mountain forests of Java (Kartawinata & Sudarmonowati, 2022). A conservation strategy for rare and endangered plant species needs to be developed. Practical conservation occurs in natural habitats. Forests are habitats for RTE species that need to protect from the threat of land clearing. The reduction of forests due to land conversion is a real threat to the existence of vulnerable species of flora and fauna (Banks-Leite et al., 2020). Sites designated as conservation areas should not be used for infra- structure development for power plants. In additi- on, other efforts to protect the RTE species in- clude monitoring the regeneration of these speci- es, such as with intensive care and monitoring. Mapping each RTE species location needs to be done for more accurate monitoring. In that study, biodiversity monitoring should be carried out by qualified consultants. The Conservation Strategy and Action Plan lists the conservation action strategy as prioritizing tree species within a certain period (Hamidi et al., 2019). Our study is expected to help add the encounter point of rare, threatened, and endangered species so that it can be used as a source of germplasm for alternatives in the propagation program of rare plant species. Schima wallichii is one of the plant species that dominates mountainous forest areas in GHS- NP, so it is common to find it growing in clumps and dominating an area (Mirmanto, 2014; Hilman & Rahman, 2021). Seedlings of S. wallichii are of ten found around the parent tree, so the individual resulting from natural regeneration and replanting can be distinguished. Meanwhile, Magnolia suma- trana is a native Java plant that can grow in mountainous areas with a few individuals (Cah- yanto et al., 2020; Tihurua & Sulistyawati, 2019). Other species with the next largest diameter were M. eminii with a diameter of 84 cm and 77 cm, then Dalrympelea sphaerocarpa with a diameter of 77 cm. The presence of M. eminii with its large size and ability to produce many fruits and seeds will threaten ecosystem sustainability because this REINWARDTIA 48 [VOL.22 species is one of the invasive alien plant species (CABI, 2022). Not only in the forest around the Gunung Salak Geothermal Power Plant unit, but the presence of M. eminii has also become a con- cern for conservation area managers because of its good adaptability in relatively large numbers, in open areas, high growth speed, many fruits, and wide distribution, causing it to grow a lot and be invasive in the Salak-Halimun corridor (Rosleine et al., 2014). The condition of the forest around the power plant shows that it is still in its growth stage, espe- cially for pioneer and introduced species with a high growth rate. Meanwhile, the native species, including RTE species, have a slower growth rate. Open areas also cause forests around the power plants to take longer to climax. The mixed forest around the power plant was formed during early construction because some forest areas had to be cleared. The pioneer plant species initially outside the power plant area spread into the area due to human activity and seed dispersal assisted by wind and animals. Several areas are still open, especially those around roads and buildings. The production activities also increase the chances of the scattering of pioneer and alien plants into the power plant area, so the forest process towards climax will run more slowly. The importance va- lue index (IVI) showed that the species could in- fluence and control the forest ecosystem through the dominance of their density and abundance. Each growth shows a different importance value index. Sellaginella plana and Miconia crenata dominate the understory, which can grow and adapt in dense forest areas. The families and spe- cies with the highest composition were the seed- lings and herbs, meaning that the understory in this forest ecosystem is still overgrown. Understo- ry growth is supported by litter from the tree around there. The litter that decomposes quickly will provide sufficient nutrients for its growth (Ainiyah et al., 2017). In addition, sunlight that can penetrate to understory also affects the diversi- ty of undergrowth (Setyawan et al., 2006; Dossa et al., 2013). Sellaginella plana had a high IVI be- cause the research location is still shaded; this fol- lows the living habitat of this species which likes shaded places and low light intensity (Krisnawati et al., 2021; Suryani et al., 2023). Miconia crena- ta, a potentially invasive introduced species, also has a growing habitat in shaded areas (De Oliveira et al., 2023). Locations with sufficient light intensi- ty tend to have higher species diversity (Destarani et al., 2017). Macaranga triloba as pioneer species domina- ted the sapling stage. It indicates that other sides of the forest around the geothermal area have opened, and the seed distribution has reached the study area. Macaranga triloba, at the seedling and sapling stage, is one of the dominant pioneer plant species associated with Schima walichii and Liquidambar excelsa in the GHSNP area, especially at an alti- tude of 1,000–1,400 m asl (Fauziah et al., 2018; Denny et al., 2021). Macaranga triloba in the se- condary forest has a reasonably high ability to ab- sorb CO2, so it can reduce emissions in the air and has the highest transpiration rate compared to other pioneer plant species around GHSNP (Mansur, 2011). The introduced species, C. houstoniana, which is relatively common at the sapling stage, also needs to be a concern for the geothermal ma- nagement area. This species has a high invasive ability, and although the population density will decrease from seedling to pole, some activities are needed to reduce the population because the dis- persal of seeds in large numbers and quickly will increase the population of seedlings and saplings in a short time (Yudaputra, 2020). Ficus fistulosa and S. wallichii dominated the pole and tree stages. Other species, such as Eurya acuminata, M. eminii, and F. padana, were also found in large numbers. The mountain of Java is habitat for S. wallichii, and this species dominates (van Steenis, 1971). The pole and tree stages are Fig. 5. Floristic structure. Density at each growth stage (A) and diameter class at the saplings and trees (B). A B IRAWAN et al.: Floristic composition and structure of vegetation in geothermal power plant, West Java. 2023] 49 commonly used as animal feed, such as M. eminii, F. fistulosa, and F. padana (Supartono et al., 2018; Nakabayashi, 2020; Priyono et al., 2020). Ficus fistulosa and F. padana were found to have high density and frequency, even though they have a small diameter. Ficus fistulosa had a diameter range of 11–29 cm, and F. padana had a diameter range of 14–35 cm. Their high fruiting ability sup- ports these two species’ high density and frequen- cy levels. They can even bear fruit throughout the year, and several animals like their syconium, so the dispersal of these two species becomes wide- spread. Ficus fistulosa and F. padana are also fo- raging sources for the javan gibbon (Hylobates moloch), which has a home range around geother- mal areas. Generally, the javan gibbon consumes the leaves and fruits of F. fistulosa and F. padana (Jang et al., 2021; Zulfa et al., 2021). Schima wallichii has a good process of rege- neration (Shrestha & Devkota, 2019). It relatively dominated the growth rate of saplings, poles, and trees, indicating that this species has relatively fast regeneration power and no disturbance from hu- mans or animals around the power plant. The na- tural rejuvenation potential of S. wallichii in Mount Merapi National Park is recorded at up to 15,000 individuals/ha. In areas disturbed by this species, as many as 500 individuals/ha can be found (Baramantya et al., 2016). Analysis of the Shannon-Wiener diversity index (H') was 3.784. Based on the index value category H', the plant diversity around the Gunung Salak Geothermal Power Plant unit was classified as high diversity. The stability of the ecosystem of a No Family Species Local name RD RF RDo IVI Seedling and herb 1 Selaginellaceae Selaginella plana Paku Rane 21.78 7.96 29.74 2 Melastomataceae Miconia crenata Harendong Bulu 10.23 10.62 20.85 3 Acanthaceae Barleria cristata Landep 13.26 3.54 16.80 4 Nephrolepidaceae Nephrolepis biserrata Paku Pedang 7.01 6.19 13.20 5 Acanthaceae Strobilanthes filiformis Bubukuan 5.87 2.65 8.53 Sapling 1 Euphorbiaceae Macaranga triloba Mara 9.30 11.29 20.59 2 Fabaceae Calliandra houstoniana Kaliandra Beureum 13.95 3.23 17.18 3 Moraceae Ficus fistulosa Kondang 8.14 8.06 16.20 4 Theaceae Schima wallichii Puspa 8.14 6.45 14.59 5 Actinidiaceae Saurauia pendula Ki Leho 4.65 6.45 11.10 Pole 1 Moraceae Ficus fistulosa Kondang 18.07 8.20 17.00 43.27 2 Pentaphylacaceae Eurya acuminata Ki Menir 13.25 8.20 15.46 36.91 3 Theaceae Schima wallichii Puspa 12.05 11.48 9.83 33.35 4 Moraceae Ficus padana Hamerang Badag 4.82 6.56 6.56 17.93 5 Magnoliaceae Magnolia sumatrana Maglid 4.82 3.28 4.93 13.03 Tree 1 Theaceae Schima wallichii Puspa 18.55 13.83 22.56 54.90 2 Rhamnaceae Maesopsis eminii Kayu Afrika 8.06 5.32 16.89 30.27 3 Moraceae Ficus padana Hamerang Badag 11.29 6.38 4.37 22.04 4 Rutaceae Melicope lunu-ankenda Ki Sampang 5.65 5.32 4.59 15.59 5 Altingiaceae Liquidambar excelsa Rasamala 4.03 5.32 3.74 13.09 Tabel 2. Importance Value Index each growth stage Note: RD: Relative Density; RF: Relative Frequency; RDo: Relative Dominance; IVI: Importance Value Index. REINWARDTIA 50 [VOL.22 place will increase along with the high value of the flora diversity index at that location (Michael, 1984). The species richness index of 16.391, indi- cates that the Gunung Salak Geothermal Power Plant unit species are in the high category. The number of species affects the value of the species richness index in a study area (Ismaini et al., 2015). The species evenness index was 0.802, and the dominance index value was low as 0.042. All diversity indices show that several species have the potential to be found growing evenly but have a very low population size, so they are not able to dominate in the study area. Based on the results and discussion, the forest ecosystem in the Gunung Salak Geothermal Power Plant area is in a good category for the composi- tion of flora and diversity index. However, inva- sive plant species' presence requires regular maintenance control. Regular monitoring is neces- sary for areas overgrown with invasive species. The mature rare, threatened, and endangered trees must be conserved to for growing well and become parent tree for plant conservation in that location. The presence of pioneer species also increases the diversity of plant species around the geothermal area, especially in preserving several plant species used as wild animal feed found at the study site. CONCLUSION In conclusion, the floristic composition and structure of vegetation on the Gunung Salak Geo- thermal Power Plant unit indicate good ecosystem conditions. Floristic composition is recorded in as many as 56 families of 110 species. The plants are found as native and introduced species. In addition, other native species were found, including Puspa (Schima wallichii) and Rasamala (Liquidambar excelsa). Introduced species around the study site include Maesopsis eminii and Calliandra houstoni- ana. Both introduced species have the potential to become invasive plants, so the spread of these spe- cies needs to be continuously monitored so that they do not become a threat to rare plants found in these locations, such as A lpinia scabra (EN), Castanopsis argentea (EN), Dipterocarpus has- seltii (EN), Lithocarpus indutus (VU), and Macropanax concinnus (VU). The vegetation structure around the study site also shows the good condition of forest regeneration, as indicated by the inverted J-curve shape for the growth stage and class diameter. The results of the IVI analysis showed that pioneer plants generally dominated the undergrowth and sapling stage. In contrast, moun- tain rainforest plants, such as S. wallichii, Ficus padana, and L. excelsa, dominated the pole and tree stages. ACKNOWLEDGEMENTS The authors would like to thank to Fikri Aziz Maulana for helping us to collect data. 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