Judul: Diversity of Petai in Central Sumatra
Abstrak: Petai (Parkia speciosa Hassk.) merupakan salah satu jenis Parkia yang paling dikenal dan mudah dijumpai. Tanaman ini tersebar di Indonesia, Brunei Darussalam, Semenanjung Malaysia, Filipina, dan Thailand. Di Indonesia petai tumbuh pada ketinggian 0-1400 m dpl. Petai merupakan tanaman yang memiliki biji beraroma khas dan banyak dimanfaatkan masyarakat sebagai lalap dan bumbu. Petai selama ini memiliki banyak potensial yang harus dipelajari, khususnya keanekaragaman dan pemanfaatannya, tetapi informasi tersebut belum sepenuhnya terungkap. Penelitian ini bertujuan untuk mengetahui keanekaragaman dan distribusi petai di Sumatera tengah berdasarkan ciri morfologi. Pengambilan 29 aksesi petai dilakukan pada bulan Juli 2017 hingga Februari 2019 di Sumatera Barat, Riau, dan Jambi. Informasi tentang keberadaan petai di lapang diperoleh dengan menggunakan metode jelajah serta mewawancarai masyarakat dan pedagang petai di pasar. Sampel petai yang diambil yaitu cabang berdaun, perbungaan dan buahnya. Karakterisasi morfologi dan identifikasi spesimen petai dilakukan di lapangan dan Laboratorium Botani, Departemen Biologi, FMIPA UNRI. Pengamatan ciri morfologi dilakukan menggunakan 40 ciri morfologi menggunakan analisis Similarity for Qualitative Data (SIMQUAL), dengan indeks keserupaan Simple Macthing (SM) dan dikelompokkan dengan metode Unweighted Pair group Method with Arithmetic Average (UPGMA). Selanjutnya 40 ciri morfologi diseleksi kembali berdasarkan prinsip mudah dilihat serta, keberagaman, keseragaman and stabil (DUS). Hasil pemilihan yaitu 9 ciri morfologi yang selanjutnya dianalisis kembali hubungan keeratannya dengan menggunakan metode UPGMA. Petai di Sumatera bagian tengah bervariasi pada ciri kulit batang luar, bentuk helaian anak daun dan ujung anak daun, perbungaan, polong, dan biji. Hasil analisis 29 aksesi petai menggunakan 40 ciri dan 9 ciri morfologi terpilih menunjukkan bahwa petai digolongkan menjadi 2 kelompok utama. Kelompok A mengacu kepada jenis Parkia speciosa Hassk. yaitu petai “Baluru”, “Gabak”, “Padi” dan “Papan”, sedangkan kelompok B mengacu kepada jenis Parkia singularis yaitu petai “Langsono”. Kajian terhadap hasil pengelompokkan menunjukkan bahwa petai dari Suamatera bagian tengah tergolong kedalam kultivar lokal. Hasil ini dapat dijadikan titik awal dalam menggolongkan petai kedalam batas-batas kultivar yang bertujuan untuk melakukan pengembangan dan pemanfaatan petai dengan landasan yang lebih kuat. Untuk itu penelitian lanjutan melibatkan segi agronomi perlu dilakukan., Petai (Parkia speciosa Hassk.) is one of the best known species and easy to find of Parkia. Naturally, petai is distributed in Indonesia, Brunei Darussalam, Peninsular Malaysia, Philippines, and Thailand. In Indonesia, this species ecologically grows at an altitude of 0-1400 m asl. Petai has a distinctive aroma. People often use petai for salad and seasoning. Petai still has a lot of potentials to be studied especially for its diversity and benefits, but information about its diversity and benefit has not been fully revealed. This study aims to determine the diversity and distribution of petai in Central Sumatra based on morphological characteristics. The collection of 29 petai accession was conducted from July 2017 to February 2019 in West Sumatra, Riau and Jambi. Information about the existence of petai in the field was obtained by using exploration methods as well as interviewing people and petai traders in the market. Petai samples taken were leafy branches, inflorescences, and fruit. Morphological characterization and identification of petai specimens were carried out in the field and Botanical Laboratory, Department of Biology, FMIPA UNRI. Observation
Keyword: “Papan”, Parkia singularis, Parkia speciosa Hassk., Petai

Judul: Analysis of Potential Non-Timber Forest Products in North Sumatra
Abstrak: Sumatera Utara memiliki potensi Hasil Hutan Bukan Kayu yang besar karena memiliki kawasan hutan yang luas. Komoditas HHBK di Sumatera Utara masih belum dimanfaatkan secara optimal. Tujuan penelitian ini mengetahui jenis HHBK yang berpotensi di Sumatera Utara. Jenis-jenis HHBK yang tercatat di Dinas Kehutanan Provinsi Sumatera Utara yaitu getah pinus, rotan manau, daun nilam, biji rotan, cengkeh, daun cengkeh, rotan sega (taman), rotan semambu, madu, dan nira. Data dan informasi diperoleh melalui hasil data sekunder yang berasal dari Dinas Kehutanan Sumatera Utara, situs internet resmi Badan Pusat Statistik Sumatera Utara, jurnal serta buku pustaka yang mendukung. Hasil penelitian menunjukkan jenis HHBK yang paling berpotensi pada saat ini di Sumatera Utara adalah getah pinus karena getah pinus memiliki Provisi Sumber Daya Hutan (PSDH) yang meningkat setiap tahunnya. PSDH yang dihasilkan getah pinus di Sumatera Utara dapat menambah pemasukan pendapatan Provinsi Sumatera Utara dan didukung oleh tempat tumbuh yang sesuai untuk pertumbuhan pinus berdasarkan kondisi iklim dan edafis., North Sumatra has great potential for non-timber forest products (NTFP) because it has a large forest area. NTFP commodities in North Sumatra are still not used optimally. The purpose of this study was to determine the types of NTFPs that have the potential in North Sumatra. The types of NTFPs recorded at the North Sumatra Provincial Forestry Service are pine resin, manau rattan, patchouli leaves, rattan seeds, cloves, clove leaves, sega (taman) rattan, semambu rattan, honey, and nira. Data and information were obtained through secondary data from the North Sumatra Forestry Service, the official website of the Central Statistics Agency of North Sumatra, journals and books that support. The results showed that currently the most potential NTFP species in North Sumatra is pine resin because pine resin has a Forest Resource Provision (FRP) which increases every year. FRP produced by pine resin in North Sumatra can increase the income of the Province of North Sumatra and is supported by suitable growing places for pine growth based on climatic and edaphic conditions.
Keyword: NTFPs, pine resin, FRP, potential

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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