Judul: Abundance and Diversity of Soil Surface Arthropods in Revegetated Land at PT. Bukit Asam, South Sumatera
Abstrak: Arthropoda permukaan tanah adalah salah satu hewan penting dalam komunitas terestrial lahan pasca tambang. Penelitian bertujuan menganalisis kelimpahan dan keanekaragaman arthropoda permukaan tanah pada lahan revegetasi di PT Bukit Asam. Metode pengumpulan data dilakukan dengan pitfall trap pada lahan revegetasi angsana (Pterocarpus indicus), merbau (Intsia palembanica), sengon buto (Enterolobium cyclocarpum) berumur 8 tahun serta hutan sekunder sebagai ekosistem kontrol, dilanjutkan dengan pengukuran kondisi lingkungan, identifikasi arthropoda, dan analisis data. Hasil penelitian menunjukkan bahwa ditemukan sebanyak 17 ordo 51 famili 118 morfospesies dengan total 4.802 individu. Lahan revegetasi angsana memiliki nilai kelimpahan dan keanekaragaman arthropoda permukaan tanah tertinggi dengan indeks keanekaragaman jenis (H’) 2,782. Sementara hutan sekunder memiliki nilai kelimpahan dan keanekaragaman jenis terendah dengan indeks (H’) 1,959. Kelimpahan arthropoda permukaan tanah didominasi oleh Ordo Hymenoptera. Adapun ordo yang paling sedikit dijumpai adalah Thysanoptera. Faktor lingkungan memiliki korelasi terhadap kelimpahan arthropoda permukaan tanah., Land surface arthropods are one of the most important animals in the terrestrial community of post-mining land. The study aimed to analyze the abundance and diversity of soil surface arthropods on revegetation land at PT Bukit Asam. Data collection methods were carried out with pitfall traps on 8-year-old angsana (Pterocarpus indicus), merbau (Intsia palembanica), sengon buto (Enterolobium cyclocarpum) revegetation land and secondary forest as a control ecosystem, followed by measurement of environmental conditions, arthropod identification, and data analysis. The results showed that there were 17 orders 51 families 118 morphospecies with a total of 4.802 individuals. The angsana revegetation land had the highest abundance and diversity of ground surface arthropods with a species diversity index (H') of 2,782. Meanwhile, secondary forest has the lowest abundance and diversity of species with an index (H') of 1,959. The abundance of soil surface arthropods is dominated by Hymenoptera Order. The least common orders were Thysanoptera. Environmental factors have a correlation with the abundance of arthropods.
Keyword: Pertambangan, Pitfall trap, Reklamasi, Serangga tanah

Judul: Macrofauna Soil Diversity in Land Cover of Revegetation Areas at PT. Bukit Asam
Abstrak: Makrofauna tanah merupakan salah satu bioindikator dalam menganalisis perbaikan lahan pascatambang. Penelitian ini diharapkan mampu memberikan informasi mengenai pengaruh tutupan lahan terhadap makrofauna tanah di lahan revegetasi PT Bukit Asam. Penelitian ini dilaksanakan pada empat jenis lahan, yaitu lahan hutan merbau, hutan angsana, hutan sekunder, dan lahan kosong. Hasil uji Beda Nyata Terkecil (BNT) menunjukkan bahwa hutan merbau memiliki kelimpahan fauna tertinggi yaitu 79 individu/m2 dan lahan kosong memiliki kelimpahan fauna terendah yaitu 0 individu/m2. Hutan merbau terbukti berbeda nyata dengan lahan kosong pada selang 95%, sedangkan hutan angsana dan hutan sekunder tidak berbeda nyata. Kerapatan vegetasi yang paling rapat memiliki pengaruh terhadap jumlah fauna tanah yang ditemukan. Parameter klimatis yang memiliki tingkat korelasi sangat kuat dan kuat adalah intensitas cahaya dan suhu lingkungan. Parameter edafis yang memiliki tingkat korelasi sangat kuat dan kuat adalah bulk density, porositas, pH, C-Organik, dan respirasi tanah., Soil macrofauna is one of the bioindicators in analyzing post-mining land improvement. This research is expected to provide information on the influence of land cover types on macrofauna abundaced in the reforested land of PT Bukit Asam. This study was conducted on four types of land: merbau forest land, angsana forest land, secondary forest land, and vacant land. The results of the BNT test showed that merbau forest had the highest fauna abundance, with 79 individuals/m2, while vacant land had the lowest fauna abundance, with 0 individuals/m2. Merbau forest was significantly different from vacant land at the 95% confidence interval, while angsana forest and secondary forest did not show significant differences. The densest vegetation density has an influence on the number of soil fauna found. Climatic parameters with very strong and strong correlation levels are light intensity and environmental temperature. Edaphic parameters with very strong and strong correlation levels are bulk density, porosity, pH, Organic Carbon, and soil respiration.
Keyword: edafis, klimatis, lahan pascatambang, vegetasi

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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