Judul: Studi Populasi Dan Distribusi Orangutan Sumatera (Pongo Abelii) Di Hutan Penyangga Dan Koridor Batang Toru Sumatera Utara
Abstrak: Populasi orangutan terus menurun dari waktu ke waktu. Penurunan ini disebabkan oleh kehilangan habitat, fragmentasi, konversi lahan dan perburuan. Salah satu habitat yang berpotensi bertahan dalam jangka panjang adalah populasi Batang Toru (Tapanuli, Sumatera Utara) yang mendukung populasi di Selatan Danau Toba. Jumlah populasi yang rendah, kehilangan habitat dan perburuan adalah beberapa faktor yang mengancam kelangsungan jangka panjang populasi orangutan Batang Toru. Habitat yang tumpang tindih serta tidak berstatus lindung berpotensi memicu konflik orangutan dan masyarakat. Hal ini sangat bertentangan dengan usaha konservasi orangutan karena orangutan memerlukan blok-blok hutan yang luas untuk menjelajah, mencari makan dan bereproduksi. Salah satu upaya konservasi yang dapat dilakukan untuk menjaga kelangsungan hidup jangka panjang orangutan di Batang Toru yaitu dengan membuat hutan penyangga dan koridor. Hutan Sitandiang, Hutaimbaru, Hopong, dan Bulu Mario adalah beberapa lokasi potensial sebagai koridor dan hutan penyangga. Data populasi dan distribusi penting sebagai data dasar untuk mencari tahu kondisi terkini orangutan dan habitatnya di lokasi tersebut. Penelitian ini bertujuan untuk menganalisis populasi dan sebaran orangutan di hutan penyangga dan potensi koridor Batang Toru Sumatera Utara. Penelitian dilakukan di hutan yang berpotensi sebagai penyangga hutan Batang Toru blok Barat (Sitandiang dan Hutaimbaru) dan hutan yang berpotensi sebagai koridor yang menghubungkan CA. Dolok Sipirok - Hutan Batang Toru blok Timur (Hopong) dan Batang Toru blok Barat – CA. Dolok Sibualbuali (Bulu Mario). Penelitian dilakukan pada bulan Juni 2015 – Pebruari 2016. Pengambilan data populasi orangutan dilakukan dengan metode penghitungan sarang dan line transect. Pengambilan data kelimpahan tumbuhan berbuah dan Ficus dilakukan dengan menggunakan metode fruit trail dan line transect. Pengambilan data vegetasi dilakukan dengan dua metode, yaitu metode petak kuadrat pada hutan tidak terganggu dan rapid assesment pada hutan terganggu. Kepadatan orangutan, tumbuhan berbuah, dan Ficus dianalisis dengan persamaan dasar van Schaik et al. 1995 Data kondisi vegetasi disajikan secara kuantitatif dengan menampilkan nilai Indeks Nilai Penting dan daftar potensi pohon pakan. Uji korelasi Pearsons digunakan untuk mengetahui korelasi antara kepadatan orangutan, tumbuhan berbuah, dan ficus. Pemetaan sarang orangutan dianalisis dengan menggunakan software ArcGIS 9.3. Penelitian ini menunjukkan kepadatan dan distribusi orangutan dipengaruhi oleh kondisi hutan, tingkat ancaman, dan ketersediaan tumbuhan berbuah. Sarang ditemukan lebih sedikit secara signifikan di daerah yang terganggu (Hutaimbaru dan Bulu Mario) daripada daerah tidak terganggu (Sitandiang dan Hopong) dengan nilai kepadatan di berturut-turut 0.2 ind/km2, 0.1 ind/km2, 0.7 ind/km2, dan 0.4 ind/km2. Jarak penemuan sarang dengan pemukiman, jalan, dan kebun sangat mempengaruhi kepadatan orangutan di lokasi penelitian. semakin dekat jarak pemukiman, jalan, dan kebun maka kepadatan orangutan semakin rendah. Hutan Hutaimbaru dan Bulu Mario merupakan lokasi dengan tingkat ancaman yang tinggi karena berbatasan langsung dengan perkebunan yang dikelola secara aktif oleh masyarakat. Kepadatan orangutan berkorelasi positif dengan kepadatan tumbuhan berbuah, namun berkorelasi negatif dengan kepadatan ficus. Sarang orangutan tidak hanya ditemukan di kawasan lindung, namun juga di luar kawasan lindung. Orangutan yang ditemukan di luar kawasan lindung ini menghadapi berbagai ancaman serius. Peningkatan status hutan dan manajemen konservasi pada lokasi penelitian penting dilakukan untuk kelangsungan jangka panjang orangutan.
Keyword: Batang Toru, distribusi orangutan, kepadatan orangutan, koridor, Pongo abelii

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: 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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