Judul: Medicinal Plants Diversity on Sago Stands in Siberut National Park, West Sumatera
Abstrak: Tumbuhan obat dapat ditemukan pada berbagai tipe habitat termasuk tegakan sagu yang banyak dijumpai di Taman Nasional Siberut. Tujuan dari penelitian ini yaitu mengidentifikasi, mendeskripsikan dan menganalisis keanekaragaman spesies tumbuhan, bentuk pemanfaatan tumbuhan obat oleh masyarakat adat Mentawai, ketersediaan tumbuhan obat dan potensi pemanfaatan tumbuhan obat pada tegakan sagu di Taman Nasional Siberut. Kegiatan penelitian dilaksanakan pada Januari‒Maret 2022 di Dusun Sakaladhat, Desa Simalegi, Kecamatan Siberut Barat dan Dusun Ukra, Desa Malancan, Kecamatan Siberut Utara dengan metode analisis vegetasi, wawancara dan observasi lapang. Terdapat 193 spesies tumbuhan dari 64 famili pada tegakan sagu. Sebanyak 60 spesies dari 31 famili telah dimanfaatkan masyarakat sebagai bahan obat sementara 55 spesies dari 36 famili berpotensi untuk dimanfaatkan sebagai bahan obat. Pemanfaatan tumbuhan obat oleh sikerei dan siagai laggek yang merupakan dukun atau ahli pengobatan di Dusun Sakaladhat dilakukan sesuai dengan pengetahuan yang diperoleh dari mimpi sementara itu pemanfaatan di Dusun Ukra disesuaikan dengan keahlian masing-masing yang diperoleh dari mimpi dan warisan turun-temurun. Ketersediaan tumbuhan obat pada tegakan sagu dapat mencukupi kebutuhan untuk mengobati 36 jenis penyakit yang diderita oleh masyarakat untuk jangka waktu 1 tahun. Penelitian ini diharapkan dapat memberikan sumbangan pengetahuan mengenai pemanfaatan tumbuhan obat pada tegakan sagu oleh masyarakat tradisional., Medicinal plants exist at various habitats including sago stands in Siberut National Park (SNP). This study aims to identify, describe, and analyze of species diversity, utilization types, availability and latent utility of medicinal plants on sago stands by Mentawai community in SNP. This research was conducted in January-March 2022 at Sakaladhat Hamlet, Simalegi Village and Ukra Hamlet, Malancan Village by carrying out vegetation analysis, interview and observation. Results show that 193 species from 64 families were found on sago stands. People have availed of 60 species from 31 families as temporary medicine while other 55 species from 36 families have potential use as remedy. Medicinal plants usage by sikerei and siagai laggek as local physicians in Sakaladhat gained purely from their spiritual dreams. Meantime, different approach of those physicians in Ukra corresponds with each ability from spiritual dreams and local knowledges passed through generations. This research reveals that these medicinal plants are sufficient enough to cure 36 illnesses for a year long. This research, in turn, may contribute to better understanding on sago’s stands medicinal plants utility by local community.
Keyword: diversity, local knowledge, medicinal plant, sago stands

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: 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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