Keanekaragaman dan Ekologi Tumbuhan Paku di Hutan Kerangas Cendil dan Hutan Hujan Tropis Gurok Beraye, Pulau Belitung

Abstract

Satu lingkungan yang unik dan membentuk banyak ekosistem di Pulau Belitung selain hutan hujan tropis adalah hutan kerangas. Hutan tipe ini tumbuh di atas tanah podsolik yang miskin unsur hara dengan pH rendah. Hutan ini didominasi oleh vegetasi semak hingga tiang termasuk tumbuhan paku. Tumbuhan paku dapat dijadikan sebagai indikator kualitas suatu ekosistem hutan karena bersifat kosmopolitan dan memiliki daya adaptasi yang sangat baik terhadap berbagai habitat. Sejauh ini belum ada kajian mengenai perbandingan keanekaragaman dan ekologi tumbuhan paku pada dua ekosistem yang berbeda, hutan kerangan dan hutan hujan tropis, di pulau Belitung. Tujuan penelitian ini adalah melakukan inventarisasi dan identifikasi keanekaragaman jenis tumbuhan paku dan menganalisis parameter-parameter ekologi tumbuhan paku di hutan kerangas Cendil dan hutan hujan tropis Gurok Beraye, Pulau Belitung. Serangkaian kegiatan dilakukan dalam penelitian ini untuk mengumpulkan data keanekaragaman dan ekologi Tumbuhan paku. Tahap pertama adalah pengambilan data keanekaragaman menggunakan metode jelajah. Penjelajahan wilayah dilakukan di hutan kerangas Cendil dan hutan hujan tropis Gurok Beraye, pulau Belitung. Data ekologi dikumpulkan degan metode sampling bertujuan. Pada lokasi ditemukannya tumbuhan paku dibuat petak contoh berukuran panjang 50 m dan dibuat plot dengan masing-masing plot berukuran 5 x 5 m berselang-seling di kanan dan kiri transek. Iklim mikro yang diukur pada tiap plot meliputi intensitas cahaya (Lux), suhu (oC), kelembapan (%Rh), dan kecepatan angin (m/s). Selanjutnya dilakukan pengamatan ciri morfologi tumbuhan paku. Ciri struktur vegetatif yang diamati meliputi habitus, tipe alat lekat, permukaan dan bentuk stipe serta rakis, tipe, bentuk, dan ukuran ental. Struktur generatif yang diamati adalah lokasi dan bentuk sori, keberadaan dan bentuk indusium, keberadaan sporangium, tipe dan bentuk spora, bentuk, ukuran, tipe laesura, dan tipe ornamentasi. Data morfologi disusun dalam bentuk deskripsi dan kunci identifikasi. Analisis data ekologi menggunakan Indeks Nilai Penting (INP), Standar Dominansi Rasio (SDR), indeks keanekaragaman Shannon-Wiener (H’), indeks kekayaan Margalef (R), indeks kemerataan (E), indeks similaritas Sorensen (IS), dan indeks distribusi Morisita (Id). Data korelasi faktor lingkungan terhadap keberadaan jenis tumbuhan paku di kedua tipe hutan dianalisis menggunakan software R Studio versi 4.0.2 dengan metode Cannonical Correspondence Analysis (CCA) yang divisualisasikan dalam bentuk grafik. Sebanyak 31 jenis tumbuhan paku yang termasuk dalam 14 suku ditemukan di hutan kerangas Cendil dan hutan hujan tropis Gurok Beraye. Suku dan jumlah jenis tumbuhan paku yang ditemukan adalah Polypodiaceae (4 jenis), Pteridaceae (4 jenis), Athyriaceae (3 jenis), Selaginellaceae (3 jenis), Thelypteridaceae (3 jenis), Blechnaceae (2 jenis), Gleicheniaceae (2 jenis), Lycopodiaceae (2 jenis), Taenitidaceae (2 jenis), Tectariaceae (2 jenis), Adiantaceae (1 jenis), Aspleniaceae (1 jenis), Dennstaedtiaceae (1 jenis), dan Nephrolepidaceae (1 jenis). Spora Tumbuhan paku yang ditemukan bervariasi pada bentuk, tipe laesura, ukuran dan rasio polar ekuatorial, serta ornamentasi spora. Spora dengan bentuk semi angular mendominasi dari 8 jenis tumbuhan paku. Tipe laesura yang ditemukan terdiri dari tipe monolete (17 jenis) dan trilete (12 jenis). Kategori ukuran spora yang teramati terbagi dalam tiga kategori yaitu kecil (10−25 μm) pada 1 jenis, medium (25−50 μm) dan besar (50−100 μm) pada 14 jenis tumbuhan paku. Tingkatan bentuk spora juga dapat ditentukan berdasarkan rasio perbandingan antara panjang kutub polar dan kutub ekuatorial. Rasio P/E menghasilkan angka yang beragam berkisar antara 0,44−0,96. Bentuk yang teramati terdiri dari peroblate (<0,50) pada 1 jenis, oblate (0,50−0,75) pada 13 jenis, suboblate (0,75−0,88) pada 8 jenis, dan oblate bulat (0,88−1,00) pada 7 jenis. Tipe ornamentasi yang dominan adalah tipe psilate (17 jenis), diikuti rugate (4 jenis), granulate (3 jenis), papillate (2 jenis), tuberculate (2 jenis), dan verrucate (1 jenis). Tumbuhan paku yang ditemukan di hutan hujan tropis Gurok Beraye lebih banyak jumlahnya (30 jenis) dibandingkan dengan di hutan kerangas Cendil (9 jenis). Tumbuhan paku di hutan hujan tropis Gurok Beraye didominasi oleh Blechnopsis finlaysoniana (dengan nilai SDR 10,44%), Dicranopteris splendida (6,36%), dan B. orientalis (5,98%), sedangkan di hutan kerangas Cendil didominasi oleh D. linearis (48,87%), Palhinhaea cernua (26,46%), dan D. splendida (14,22%). Parameter ekologi yang mempengaruhi keanekaragaman dan kelimpahan tumbuhan paku meliputi suhu, intensitas cahaya, kelembapan, dan ketinggian tempat. Keberadaan tumbuhan paku di hutan kerangas Cendil seperti Lycopodium clavatum dipengaruhi oleh suhu, sedangkan P. cernua dipengaruhi oleh kelembapan dan ketinggian, sementara di hutan hujan tropis Gurok Beraye jenis Thelypteris aspera dan Pteris semipinnata dipengaruhi oleh kelembapan dan suhu, sedangkan Diplazium angustipinna, P. cernua, P. vittata, Selaginella ciliaris dan Tectaria heracleifolia dipengaruhi oleh ketinggian. Kata kunci: analisis korespondensi kanonik, ekoton, Pteridophyta, spora, standar dominansi rasio

One unique environment that forms many ecosystems on Belitung Island apart from the tropical rain forest is the heath forest. This type of forest grows on nutrient-poor podzolic soils with a low pH. This forest is dominated by shrubs and poles, including pteridophytes. Pteridophytes can be used as an indicator of the quality of a forest ecosystem because they are cosmopolitan and have excellent adaptability to various habitats. So far, there has been no study on the comparison of the diversity and ecology of pteridophytes in two different ecosystems, the heath forest and the tropical rain forest, in Belitung island. The purpose of this study was to carry out an inventory and identification of the diversity of pteridophyte species and to analyze the bioecological parameters of pteridophytes in the Cendil heath forest and the Gurok Beraye tropical rain forest, Belitung island. A series of activities were carried out in this study to collect diversity and ecological data of pteridophytes. The study began with the collection of diversity data using the roaming method. Exploration of the areawas carried out in the Cendil heath forest and the Gurok Beraye tropical rain forest areas, Belitung island. Ecological data were collected using purposive sampling method. At the location where pteridophytes were found, sample plots were made with a length of 50 m and several plots were made with each plot measuring 5 x 5 m alternating on the right and left of the transect. The microclimate measured in each plot included light intensity (Lux), temperature (oC), humidity (%Rh), and wind speed (m/s). Furthermore, observations were made to observe the morphological characteristics of pteridophytes. The observed vegetative characters included habitus, type of attachment organ, surface and shape of stipe and rachis; type, shape, and size of fronds. The generative structures observed were the location and shape of the sori, the presence and shape of the indusium, the presence of sporangium, the type and shape of the spores; the shape, size, type of laesura; and the type of ornamentation. Ecological data analysis used the Important Value Index (IVI), the Summed Dominace Ratio (SDR), the Shannon-Wiener diversity index (H'), the Margalef wealth index (R), the evenness index (E), the Sorensen similarity index (IS), and the Morisita distribution index (Id). Correlation data of environmental factors on the presence of pteridophytes in the Cendil heath forest and Gurok Beraye tropical rain forest were analyzed using R Studio software version 4.0.2 with the Canonical Correspondence Analysis (CCA) method which was visualized in a graphic. A total of 31 species of pteridophytes belonging to 14 families were found in the Cendil heath forest and the Gurok Beraye tropical rain forest. The families and species of pteridophytes found were Polypodiaceae (4 species), Pteridaceae (4 species), Athyriaceae (3 species), Selaginellaceae (3 species), Thelypteridaceae (3 species), Blechnaceae (2 species), Gleicheniaceae (2 species), Lycopodiaceae (2 species), Taenitidaceae (2 species), Tectariaceae (2 species), Adiantaceae (1 species), Aspleniaceae (1 species), Dennstaedtiaceae (1 species), and Nephrolepidaceae (1 species). The pteridophyte spores observed were varied in the shape, type of laesura, size and ratio of the equatorial polar, and spore ornamentation. Semi-angular spores dominate in eight species. The type of laesura found consisted of monolete found in 17 species and trilete found in 12 species. The observed spore sizes were classified into two categories, namely namely small (10−25 m) in 1 species, medium (25−50 m) and large (50−100 m) owned by 14 species. The P/E ratio produces numbers that range from 0.44 to 0.96. The observed spore forms consisted of peroblate (<0.50) onwed by one species, oblate (0.50−0.75) found in 13 species, suboblate (0.75−0.88) onwed by 8 species, and round oblate (0. 88−1.00) onwed by 7 species. The dominant ornamentation type was psilate (17 species), followed by rugate (4 species), granulate (3 species), papillate (2 species), tuberculate (2 species), and verrucate (1 species). The pteridophyte found in the Gurok Beraye tropical rain forest were more numerous (30 species) than in the Cendil heath forest (9 species). The pteridophyte in the Gurok Beraye tropical rain forest were dominated by Blechnopsis finlaysoniana (with an SDR value of 10.44%), Dicranopteris splendida (6.36%), and B. orientalis (5.98%). In comparison, the Cendil heath forest was dominated by D. linearis (45.87%), Palhinhaea cernua (23.46%), and D. splendida (16.22%). Ecological parameters that affect the diversity and abundance of pteridophyte include temperature, light intensity, humidity, and altitude. The presence of pteridophyte in the Cendil heath forest such as Lycopodium clavatum is affected by temperature, while P. cernua is affected by humidity and altitude, while in the tropical rain forest of Gurok Beraye, Thelypteris aspera and Pteris semipinnata are affected by humidity and temperature, while Diplazium angustipinna, P. cernua, P. vittata, Selaginella ciliaris and Tectaria heracleifolia affected by altitude. Keywords: canonical correspondence analysis, ecotone, Pteridophytes, spores, summed dominace ratio