Judul: Karakteristik Pohon Tempat Bersarang Orangutan Sumatera (Pongo abelii Lesson, 1827) di Kawasan Hutan Batang Toru, Kabupaten Tapanuli Utara – Sumatera Utara
Abstrak: The decline of natural habitat of Sumatran Orangutan (Pongo abelii Lesson, 1827) and persecution causing it's population decline. Batang Toru Forest has an important value as a habitat of Sumatran Orangutan which is separated from it's main habitat in Leuser Ecosystem (Aceh). Orangutan is rare species and it has preferention of choosing the nest location and the species of nesting tree with spesific characteristics. The objective of this research is to discover the characteristics of Sumatran Orangutan's nesting tree in Batang Toru Forest. The research conducted at October 23th until December 22th 2008 in Research Station Yayasan Ekosistem Lestari – Sumatran Orangutan Conservation Program (YELSOCP) in the 12,75 km2 area of West Block of Batang Toru Forest, in North Tapanuli of North Sumatera. Equipment that used are girth measuring tape, 30 m measuring tape, 20 m rope, machete, compas, flagging tape, digital camera, camera trap, thermo-hygrometer, watch, and stationary. Primary data are vegetation structure and composition, temperature and humidity, water availability, and profil of nesting tree (species of tree, total height, diameter, crown width, and crown shape), nest height, nest position, and the existence of other animals. This primary data are colected by nest survey method and vegetation analysis. Secondary data are general condition of research site and bio-ecology of Sumatran Orangutan. During the research found 154 nesting trees, it’s content 20 tree species. 33,74% (52 trees) of it is Hoting (Lithocarpus spp.). The tree height of nesting tree is about 16-20 m (34%) with average tree height from all trees is 20,35 m and average nest height in 17,24 m. In such as low nest and tree height the Orangutan's nest is covered by the taller crown of other trees from rain and wind. Orangutan tend to build their nest at tree with diameter 10-19 cm and average diameter from all the trees is 23,71 cm. The crown width less than 11 m2 with average from all the trees 15,64 m2. Orangutan's nest near the river indicated that nest location preferention caused by the location near the river is lower (the slope area). In the research location, potential competitor animal are Siamang (Symphalangus syndactilus), Gibbon (Hylobates agilis ungko), Pig-tailed monkey (Macaca nemestrina), Binturong (Arctictis binturong), squirrel (Callosciurus notatus) and Hornbill. The concultion of nesting tree characteristics are total height 16-20 m, diameter 10- 19 cm, crown width less then 11 m2, and ball shape crown. Hoting (Lithocarpus spp.) is tree species that qualify with that tree characteristics, for that reason Orangutan in Batang Toru Forest prefer to use this tree species than other tree. The location preferention is location which is covered from rain and wind.
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Judul: Preferensi Habitat Bersarang Orangutan Sumatera (Pongo abelii Lesson, 1827) di Kawasan Hutan Batang Toru Kabupaten Tapanuli Utara – Sumatera Utara
Abstrak: Habitat degradation and persecution are causes of animals extinction in Indonesia. One of them is Sumatran Orangutan (Pongo pygmaeus abelii Lesson, 1827) that now on the red list of the spesies of International Union for Conservation of Nature (IUCN) as a critically endangered species. Batang Toru Forest (BTF) is one of the last 18 habitat units of Sumatran Orangutan in Sumatera. At the present time, BTF is in initiation process of Collaborative Management Base on Sustainability of Intact Ecosystem Unit figuration. Data and information about Sumatran Orangutan (umbrella spesies of BTF) could accelerate the initiation process. One aspect that could complete the reference of Orangutan is the nesting habitat preferention. The objective of this research is discovered the nesting habitat preferention of Sumatran Orangutan at various habitat in BTF. This research conducted during Oktober-Desember 2008 at YEL-SOCP's research station, in 12,5 km2 west block area of BTF. Equipment that used are GPS, binoculars, measuring tape, camera, camera trap, map, flagging tape, stationary, rope, knife, thermometer, and hygrometer. Secondary data are bioecology of Sumatran Orangutan and general condition of research site which collected by interview and literature observation method. Primary data are Orangutan's nest frequency, which collected by the nest survey method, and the structure and composition of vegetation, which collected by vegetation analysis method. The frequency calculated by dividing the total number of nest that found with the length of the track. The structure and composition of vegetation discovered by Importance Value Index and diagram of profile vegetation. BTF's research site consist of three habitat type; peat swamp forest, upper Dipterocarp forest, and the ecoton. Peat swamp forest characterized by the high abundant of mosses and Nephentes spp., which is gradually decrease in ecoton and in upper Dipterocarp forest. Peat swamp forest has the highest vegetation density, which is also gradually decrease in ecoton and in upper Dipterocap forest. The vegetation species that identified as Orangutan's food resources in peat swamp forest are 7 species, in ecotone are 5 species, and in upper Dipterocarp forest are 4 species. The highest nest frequency found in peat swamp forest (18,7 nests/km track). It is caused by the peat swamp forest provides food resources for Orangutan, such as leaves and tree bark, troughout the year. The stand of peat swamp forest has the highest density than the other habitat, so that the estimation of actual nest frequency in peat swamp forest must be more than 18,7 nest/km track. The nest dissemination in various condition ilustrated the nest habitat preferention concerned with time. During the research, Orangutan build nest in upper Dipterocarp forest, while the old nest, found in great quantities in the peat swamp forest and ecoton. The nest can be found in each habitat, with the highest frequency found in peat swamp forest (18,7 nest/km track). This high number caused by the habitats ability to provides Orangutans food resources such as leaves and tree bark troughout the year. This habitats are intact habitat unit of Orangutan, which the stand characteristic of each habitat is not the determining factor of nesting habitat preferention. The nesting
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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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