Judul: Habitat analysis and population estimation of sumatran orangutan (Pongo abeii Lesson 1827 at the Forest of Batang Toru, North Sumatra
Abstrak: The Batang TofU forest located in North, Center and South of Tapanuli, North Sumatra was recently found as one of Sumatran orangutan population habitat. A survey of trees species, nesting behavior and population of Sumatran orangutan was carried out during October 2007 up to January 2008 and aimed to analyze: (1) the forest structure, composition and trees distribution (including feeding and nesting trees); (2) estimated density and popUlation; and (3) the threat factors influenced the survival of Sumatran orangutan in Batang TofU forest. The results of the inventory of trees with diameter at breast height (DBH) 2: 10 cm in 3.84 ha areal sampling showed that 274 species in 56 families, represented by 1,896 individuals with total basal area of 148.9 m2lha and density of 498 treeslha. This forest was richer in tree species than other lowland forests in North Sumatra, Borneo and the Malay Peninsula and was dominated by Sapotaceae trees. The most prominent species were Tristania maingayi, Casuarina sumatrana, Quercus sumatrana and Ganua motleyana in every types of forest and differenced with Batang Gadis National Park which dominated by Dipterocarps. There were 96 feeding trees species in 25 families, represented by 536 individuals with total basal area of 46.7 m2lha. The prominent heights of feeding trees were below 30 m and distributed abundantly in the old moist secondary forests. The most important feeding trees for orangutans (Diospyros sp., Eugenia sp., Nephelium sp., Lithocarpus sp., Ficus sp., Artocarpus sp., Durio sp., and Garcinia sp.) were abundantly found in the old moist secondary forests, too. Orangutans commonly prefer to nest on the top of tree bar and the main branch of trees (DBH 20-30 cm; heights 15-20 m), especially in the middle canopy (20-30 m). Considering that there were enough feeding trees in this canopy. The most preferred nesting trees genus/species were Quercus sp., Syzygium sp., Shorea sp., Diospyros sp. and Lithocarpus sp. It was also invented 267 orangutan nests along 40.125 km cumulative lengths of line transects or equal with 0.54 percent of study area conducted at 11 sites. Densities were found higher in the old moist secondary forest while it was conversely lower density in the mixed forest. The distributions of nests were tended to clumped, related to the distribution of feeding trees. Orangutan population in 748.86 km2 ha potential habitat was approximately 337-421 individuals. Their distribution was limited by elevation and food availability. Human activities such as land conversion for agriculture purposes had become important factors affecting orangutan distribution. Field fact finding showed that many orangutan direct sightings and nests were located much closer to area human activities and logging concessions. This eventually has become real and concreted threat to their remaining population. It's needed to conduct further research in long-term monitoring and develop a strategic planning which promotes community involvement for the conservation of orangutan.
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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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