Judul: Potensi Cadangan Biji dan Spora Tumbuhan Bawah Pasca Erupsi Merapi di Taman Nasional Gunung Merapi
Abstrak: Erupsi Merapi pada tahun 2010 menyebabkan kerusakan ekosistem Taman Nasional Gunung Merapi (TNGM). Kerusakan ekosistem dapat pulih secara alami melalui proses suksesi. Cadangan biji dan spora di dalam tanah menjadi sumber benih bagi keberlangsungan proses suksesi. Penelitian ini bertujuan untuk menganalisis komposisi vegetasi tumbuhan bawah dan mengeksplorasi potensi cadangan biji dan spora. Analisis vegetasi dilakukan dengan metode kuadrat di tiga lokasi yaitu terdampak erupsi berat, sedang, dan ringan. Tiga buah plot berukuran 5x5 m2 dibuat pada setiap kriteria lokasi. Tiga buah subplot berukuran 1x1 m2 dibuat pada setiap plot. Contoh tanah diambil dari subplot berukuran 1x1 m2. Contoh tanah digunakan dalam uji perkecambahan di rumah kaca. Berdasarkan indeks nilai penting, vegetasi di lokasi terdampak berat dan ringan didominasi oleh famili Poaceae, sedangkan lokasi terdampak sedang didominasi oleh Cyperaceae. Vegetasi di lokasi terdampak sedang dan ringan memiliki indeks keanekaragaman dan kemerataan jenis yang lebih tinggi dibandingkan lokasi berat. Hasil uji perkecambahan menunjukkan terdapat 34 jenis tumbuhan bawah yang berasal dari 14 famili. Kesamaan komposisi vegetasi tumbuhan bawah dengan hasil uji perkecambahan ditunjukkan dengan indeks kesamaan Sorensen rendah di lokasi terdampak berat 0.23, sedang 0.48, dan ringan 0.41.
Keyword: kerusakan ekosistem, Poaceae, suksesi, uji perkecambahan

Judul: Keanekaragaman Tumbuhan Bawah Pasca Erupsi Merapi di Taman Nasional Gunung Merapi, Yogyakarta
Abstrak: The eruption of Merapi Volcano in 2010 caused a great damage to the surrounding ecosystem. The recovery of surrounding ecosystem was done through succesional process. Organisms occur during early succesional stage are understory plants, thus they could be used as indicator of early stage succesion of damaged vegetation in Mount Merapi. The objective of this research was to describe and compare the diversity of understory plants after the eruption of Merapi Volcano in 2010 in Mount Merapi National Park, Sleman Region, Yogyakarta in two locations namely Gandok and Kaliurang Recreational Park. Gandok was categorized as high damaged location, while Kaliurang Recreational Park represented low damaged location. Vegetation was analyzed using quadratic method. Plants sample was identified in laboratory. Vegetation analysis generated the value of Significant Value Index (SVI), Diversity Index (H’), and Similarity Index (IS). Results showed that understory plant diversity of Gandok consist of 74 species and 63 genera, while Kaliurang Recreational Park consist of 49 species and 44 genera. The highest SVI was obtained by Digitaria nuda in Gandok and Brachiaria reptans in Kaliurang Recrational Park. Gandok and Kaliurang Recreational Park have a low similarity of understory community. Both location were categorized in medium diversity level.
Keyword: 

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.
Keyword: