Judul: Food Plant Diversity on Sago Stands in Siberut National Park, West Sumatera
Abstrak: Kepulauan Mentawai memiliki potensi tumbuhan pangan berlimpah yang tumbuh di berbagai jenis tegakan, salah satunya yaitu tegakan sagu. Namun, tidak semua tumbuhan pangan pada tegakan sagu tersebut telah dimanfaatkan. Penelitian bertujuan mengidentifikasi dan mendeskripsikan keanekaragaman spesies tumbuhan pangan pada tegakan sagu di Taman Nasional Siberut serta pemanfaatannya oleh masyarakat, mengidentifikasi dan menganalisis potensi tumbuhan pangan yang sudah dan belum dimanfaatkan, serta mengukur ketersediaan spesies tumbuhan pangan. Metode yang digunakan meliputi analisis vegetasi, wawancara, observasi, serta pembuatan herbarium. Hasil penelitian menunjukkan keanekaragaman spesies tumbuhan pada tegakan sagu di Dusun Sakaladhat lebih rendah dibandingkan Dusun Ukra, dengan Indeks Kesamaan Spesies rendah sebesar 43,72%. Terdapat 42 spesies tumbuhan dari 28 famili ditemukan pada tegakan sagu yang dimanfaatkan oleh masyarakat. Spesies tumbuhan yang paling banyak dimanfaatkan yaitu dari famili Zingiberaceae (7,14%), herba dan pohon (38%), buah (41%), konsumsi langsung (22%), serta kelompok buah-buahan (29%). Tumbuhan pangan potensial yang paling banyak ketersediaannya yaitu Artocarpus heterophyllus (175 orang/tahun) dan Bambusa sp. (824 orang/tahun)., Mentawai Islands store plentiful potential food plants that live on various stands, one of them is on sago stand. However, not entirely of those plants may have been utilized to their fullest potential. This study aims to identify and describe food plant species diversity on sago stands in Siberut National Park and their use by Mentawai community, identify and analyze potential food plants both have been and have not been utilized, and measure the availability of food plant species. It was conducted by vegetation analysis, interviews, field observations, and herbarium making. Results show that plant species diversity on sago stands in Sakaladhat Hamlet was lower than Ukra Hamlet, with low Species Similarity Index of 43,72%. 42 plant species from 28 families are used by the community. The most used plant species were Zingiberaceae family (7,14%), herb and tree-habitual (38%), fruit (41%), direct consumption (22%), and fruit groups (29%). The most abundant potential food plants were Artocarpus heterophyllus (175 people/year) and Bambusa sp. (824 people/year).
Keyword: food plants, sago, Siberut, species diversity

Judul: Ethnobotany Sago (Metroxylon sagu Rottb) Mentawai  people in Siberut National Park, Mentawai Islands Regency
Abstrak: Studi etnobotani merupakan ilmu yang mempelajari pengetahuan masyarakat secara tradisional terhadap keanekaragaman tumbuhan di sekitarnya serta pemanfaatan tumbuhan tersebut. Masyarakat Mentawai memanfaatkan tumbuhan sagu sebagai pangan pokok sejak nenek moyang mereka, baik untuk makanan pokok, atap rumah dan perkawinan adat. Tujuan penelitian untuk mengetahui etnobotani sagu (Metroxylon sagu Rottb), perbandingan bentuk pemanfaatan dari beberapa masyarakat dan hambatan, upaya konservasi serta rencana pengembangan sagu secara berkelanjutan oleh Masyarakat Mentawai di Taman Nasional Siberut, Kabupaten Kepulauan Mentawai. Metode pengambilan data menggunakan teknik snowball sampling. Pemanfaatan sagu oleh Masyarakat Mentawai terdiri atas daun, kulit pelepah, kulit batang, batang (empulur) dan akar. Masyarakat belum memanfaatkan sagu secara optimal serta upaya konservasi yang dilakukan agar kelestarian sagu terjaga, perlu adanya perhatian khusus dari pihak pemerintah daerah perihal fasilitas pendukung, edukasi dan pendampingan budidaya sagu., The study of ethnobotany is a science that studies traditional community knowledge of the diversity of plants in the vicinity and the use of these plants. The Mentawai people use sago plants as staple food since their ancestors, both for staple food, roofs and traditional marriages. The purpose of this study was to determine the ethnobotany of sago (Metroxylon sago Rottb), comparison of forms of use from several communities and obstacles, conservation efforts and sustainable development plans of sago by the Mentawai Community in Siberut National Park, Mentawai Islands Regency. The data collection method used snowball sampling technique. The use of sago by the Mentawai community consists of leaves, midrib bark, bark, stem (pith) and roots. The community has not utilized sago optimally and the conservation efforts that have been made to maintain the sustainability of sago, need attention from the local government for special support, education and assistance in sago cultivation.
Keyword: ethnobotany, Metroxylon sago, snowball, conservation efforts

Judul: Hamiltonian formulation for linear waves motion in two layers fluid
Abstrak: The surface wave could be considered as a wave that separates two fluids, namely water and air. Based on this assumption, it is introduced the interfacial wave, a wave between two layers of fluid with different density. The formulation of interfacial waves motion begins with deriving the base equation of irrotational ideal fluid. Furthermore, according to irrotational fluid assumption, the base equation can be stated in velocity potential. In this derivation, the fluids domain is assumed to be restricted by rigid lid boundary conditions, both at the upper and lower limit. Therefore, the interfacial waves motion can be explained in a hamiltonian formulation. In the hamiltonian formulation, total energy is defined as the sum of kinetic and potential energy. The hamiltonian system is obtained from reduction of kinetic energy by using the Dirichlet Neumann Operator. The resulted kinetic energy equation is nonlinear. Therefore, this form is linearized by first part of the Taylor expansion. This linearization gives a dispersion relation of linear wave. Based on this dispersion relation, the phase speed of the linear wave depends on the density ratio of the two layers fluid.
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