Judul: Analysis of Species Composition and Stand  Structure of Degraded Natural Forests Before and After Gap Planting in IUPHHK- HA PT. Sarmiento Parakantja Timber
Abstrak: Rehabilitasi hutan alam terdegradasi dapat dilakukan dengan penerapan teknologi tanam rumpang. Komposisi jenis dan struktur tegakan menjadi salah satu indikator lingkungan untuk mengetahui keberhasilan penerapan teknologi tanam rumpang. Penelitian bertujuan untuk mengetahui pengaruh tanam rumpang terhadap komposisi jenis dan struktur tegakan penyusun hutan. Penelitian dilakukan pada bulan Maret sampai Mei 2021 dengan metode analisis vegetasi pada tegakan sebelum dan sesudah tanam rumpang. Hasil penelitian menunjukkan bahwa komposisi jenis tegakan hutan memiliki perbedaan antara sebelum dan sesudah tanam rumpang dengan penurunan nilai kerapatan pada seluruh tingkat vegetasi, namun nilai indeks keanekaragaman hayati sesudah tanam rumpang tidak berbeda dengan sebelum tanam rumpang dengan indeks kesamaan komunitas bernilai mendekati 100%. Struktur tegakan sebelum dan sesudah tanam rumpang untuk seluruh jenis pohon membentuk kurva “J” terbalik dengan persamaan eksponensial negatif nilai R2 mendekati 1 serta nilai p-value<0,05. Penerapan teknologi tanam rumpang menggunakan areal sebesar 41,97% dari total areal plot penelitian., Rehabilitation of degraded natural forests can be carried out by applying gap planting technology. Species composition and stand structure are one of the environmental indicators to determine the success of the application of gap planting technology. The research aim is to determine the impact of gap planting on the species composition and stand structure of the forests. The research was conducted from March to May 2021 by using vegetation analysis method on before and after gap planting stand. The results showed that the species composition of forest stand had differences between before and after gap planting with a decrease in density values at all vegetation levels, but the biodiversity values index after gap planting was not different from before gap planting and the community similarity index is close to 100%. The stand structure of all tree species before and after gap planting form the "J" reversed curve and a negative exponential equation with a value of R2 close to 1 and p-value <0,05. Application of gap planting technology used 41,97% of the total research plot area.
Keyword: Hutan Alam Terdegradasi, Komposisi Jenis, Rehabilitasi, Struktur Tegakan, Tanam Rumpang

Judul: Study of Gap Planting Impact to Soil Erosion on Rehabilitation Activities of Degraded Natural Forests in the PBPH Areal of PT SARPATIM
Abstrak: Pengembangan sistem silvikultur TPTR dan TRTR memerlukan informasi dampak tanam rumpang di areal hutan alam terdegradasi yang nantinya berdampak terhadap tanah hutan, terutama erosi tanah. Tujuan penelitian untuk mendapatkan informasi tingkat erosi tanah akibat kegiatan tanam rumpang di areal hutan alam terdegradasi serta bertopografi datar-landai dan sedang. Penelitian dilaksanakan pada Mei-September 2021 dengan pengambilan data sebanyak delapan kali di enam plot tanam rumpang dan enam plot hutan alam terdegradasi. Hasil uji statistik menunjukkan bahwa terdapat perbedaan nyata perlakuan teknologi tanam rumpang terhadap besar erosi tanah. Besar erosi tanah di rumpang bertopografi datar-landai dan sedang tidak berbeda nyata. Kesimpulan penelitian menunjukkan bahwa besarnya tanah tererosi yang terjadi berturut-turut dari terbesar ke terkecil ialah pada areal hutan alam terdegradasi, jalur tanam di rumpang, dan penyekat erosi di rumpang., The development of TPTR and TRTR silvicultural systems requires information on the impact of gap planting in degraded natural forest areals that might will have an impact on forest soils, especially soil erosion. The purpose of the research was to obtain information on the level of soil erosion due to the application of gap planting in degraded natural forest areals and with flat to sloping and moderate class topography. The research was carried out in May-September 2021 with data collection eight times in six gap planting plots and six degraded natural forest plots. The results of statistical tests showed that there were noticeable differences in the treatment of gap planting technology to the magnitude of soil erosion. Meanwhile, the magnitude of soil erosion in the gap flat to sloping topography and moderate topography did not show a noticeable difference. It is concluded, that the amount of eroded soil that occurred in order from the largest to the smallest was in the degraded natural forest areal, the planting stripe in the gap, and the erosion barrier in the gap.
Keyword: Degraded natural forests, Erosion, Gap planting technology, Rehabilitation

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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