Judul: Keragaman dan Jumlah Kelompok Acari Tanah pada Kebun Kelapa Sawit di PTPN VIII Cikasungka Kabupaten Bogor
Abstrak: Oilpalm is one of the plantation commodities which have an important role in generating foreign exchange through the production of palm oil and palm kernel oil. Development of oil palm plantation in Indonesia is supported by the large areal potency, tropical climate and suitable soil. Oilpalm can grow at pH 4,0-6,0, but the optimum pH is between 5,0-5,6. Suitable pH associated with the decomposition process in ecosystems where these plants live. Soil mesofauna is one of components of the soil ecosystem. Its existence and activity in the soil can affect soil fertility. One of soil mesofauna that can be found abundantly is soil acari. Most members of the acari live in soil as well as on the soil surface. Acari has a body length between 0,1 mm to 2,0 mm. Acari body color ranging from light brown to black with varies body shapes. Acari body size will become smaller following to the depth of the soil where they lived. The objective of this study was to determine the soil acari diversity and abundance at area of palm oil productive plants (TM) and immature palm oil plants (TBM). Method of research was extraction of animal from the soil samples using Kempson Extractor, then the soil fauna especially acari was identified using a stereo microscope. Generally, three sub-orders were obtained in each area, namely suborder Oribatida, Gamazina and Uropodina. Results showed the average population of acari from TM area was 2880±1089 individuals m-2, the average population of soil acari from TBM area was 1218±392 individuals m-2. Sub order Oribatida most often found in TBM and TM, as well. From the result, it could be concluded that the older age of the plant, acari population was found to be higher, because the older plant was producing more litter than the younger plants, so it could increase population of soil microbes. Correspondence analysis showed that Gamazina affected by soil properties, pH, Cu, C-organic, N, K, KA, Zn, and Ca.
Keyword: Bogor Agricultural University (IPB), immature palm oil plants, palm oil producing plants, soil mesofauna

Judul: Jumlah dan Keanekaragaman Mikroarthopoda pada Kebun Karet dan Hutan di Cikabayan IPB, Bogor
Abstrak: ciptt Jumlah dan keanekaragaman mikroarthopoda seperti Acari dan Collembola, dapat dipengaruhi oleh penggunaan lahan dan berbagai faktor lingkungan seperti suhu tanah, pH tanah, kelembaban udara, dan bahan organik tanah. Bahan organik menjadi habitat dan bahan makanan bagi sebagian besar mikroarthopoda. Tujuan dari penelitian ini adalah untuk mengetahui jumlah dan jenis Acari dan Collembola pada tipe penggunaan lahan yang berbeda, serta mempelajari keanekaragaman Acari sampai tingkat suborder dan Collembola sampai tingkat famili. Contoh tanah diambil dari lima titik secara acak, masing-masing dari tanah kebun dan tanah hutan. Fauna tanah diekstraksi menggunakan Kempson Funnel Extractor. Hasil penelitian menunjukkan pada tanah kebun karet diperoleh total Acari sebesar 5590±1886,80 individu/m² dengan tiga subordo yaitu Oribatida, Mesostigmata, dan Prostigmata. Collembola sebesar 620±205,50 individu/m² dengan tiga famili yaitu Entomobrydae, Isotomidae, dan Onychuridae. Sedangkan pada tanah hutan diperoleh Acari sebesar 13140±6452,65 individu/m² dengan dua subordo yaitu Oribatida, dan Mesostigmata. Collembola sebesar 1860±870,26 individu/m² dengan empat famili yaitu Entomobrydae, Isotomidae, Onychuridae, dan Sminthuridae. Berdasarkan nilai Shannon's diversity index, tanah kebun memiliki keanekaragaman Acari dan Collembola tertinggi yaitu sebesar 1,38±0,71 dan pada tanah hutan sebesar 0,57±0,35. Secara umum populasi mikroarthropoda tertinggi ditemukan pada tanah hutan. Kandungan P-tersedia tanah memiliki hubungan positif dengan populasi famili Entomobrydae dan subordo Oribatida. Kandungan pH, N-total, dan C-organik memiliki hubungan positif dengan populasi famili Onychuridae dan subordo Mesostigmata. Kandungan kadar air dalam jumlah tertentu memiliki hubungan positif dengan populasi famili Isotomidae, sedangkan subordo Prostigmata tidak berpengaruh terhadap kondisi tanah.
Keyword: Mikroarthopoda, Acari, Collembola, Shannons diversity index, Temperature, Enthomorbrydae, Soil fatwa, Forest soil, Mesostiqmata, Isotomidae, Onycluridae

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: