Judul: Pendugaan Cadangan Karbon pada Lahan Revegetasi di PT.  Pesona Khatulistiwa Nusantara, Kabupaten Bulungan,  Kalimantan Utara.
Abstrak: Perubahan iklim disebabkan oleh meningkatnya gas rumah kaca (GRK) yang ada di atmosfer, utamanya gas karbon dioksida (CO2). Peningkatan ini dikarenakan banyaknya deforestasi dan degradasi hutan, salah satunya kegiatan pertambangan batubara dengan sistem terbuka. Pertambangan tidak akan berdampak buruk jika dilakukan revegetasi yang dapat berperan dalam upaya peningkatan penyerapan CO2. Dalam hal ini pemantauan cadangan karbon perlu dilakukan secara reguler. Penelitian ini bertujuan untuk menduga total cadangan karbon dan menganalisis kontribusi kerapatan pohon, luas bidang dasar, dan H’ terhadap cadangan karbon di lahan revegetasi pascatambang batubara PT. Pesona Khatulistiwa Nusantara. Metode yang digunakan yaitu stratified systematic sampling with random start dengan menggunakan plot lingkaran sebesar 17,84 m. Analisis yang digunakan pada penelitian ini antara lain indeks nilai penting, H’, dan dilakukan uji-t Student serta analisis korelasi pada perangkat lunak R studio. Pendugaan total cadangan karbon (t C/ha) pada lahan revegetasi berdasarkan tahun tanam 2013 sampai 2019 berkisar antara 41,02 t C/ha hingga 151,88 t C/ha. Hasil uji korelasi Pearson antara kerapatan pohon dan total cadangan karbon sebesar 0,851, dan uji korelasi Pearson antara luas bidang dasar dan total cadangan karbon sebesar 0,790., Climate change is caused by increased greenhouse gases (GHGs) in the atmosphere, mainly carbon dioxide (CO2). This increase is due to the large amount of deforestation and forest degradation, including coal mining with an open pit mining system. Mining will not have a bad impact if revegetation is carried out properly. Revegetation plays an important role in efforts to increase carbon stock and sequestration. However, regular monitoring of carbon stock and equestration is necessary. This study aimed to estimate the total carbon stock and analysed the contribution of tree density, basal area, and H’ to carbon stock in revegetation land after coal mining of PT. Pesona Khatulistiwa Nusantara. The method used was stratified systematic sampling with random start using a circle plot of 17.84 m. The analyses used in this study included the following parameters: importance value index and H’, while Student's t-test and correlation analysis were conducted on R studio software. Estimates of total carbon stocks (t C/ha) on revegetation land based on planting years 2013 to 2019 ranged from 41.02 t C/ha to 151.88 t C/ha. The result of Pearson correlation test between tree density and total carbon stock was 0.851, and Pearson correlation test between basal area and total carbon stock was 0.790.
Keyword: Analisis vegetasi, biomassa, karbon.

Judul: Understory Plant Diversity and Carbon Stock Potential in Post-Mining Revegetation Land at PT. Berau Coal East Kalimantan
Abstrak: Inventarisasi tumbuhan dan perhitungan karbon dilakukan untuk mengukur keberhasilan revegetasi lahan pascatambang. Penelitian ini bertujuan untuk mengetahui keanekaragaman tumbuhan bawah serta mengetahui potensi simpanan kabon di atas permukaan tanah serta kaitannya terhadap perbedaan umur lahan revegetasi 2018, 2016 dan 2013. Pembuatan plot menggunakan metode petak contoh berukuran 50 m x 50 m sebanyak 3 plot pertegakan umur. Masing-masing plot terdapat 4 (subplot). Pengukuran biomassa dilakukan dengan metode non destruktif dan menggunakan rumus alometrik. Hasil penelitian menunjukkan keanekaragaman ketiga umur revegetasi yang tidak jauh berbeda. Biomassa total dan kandungan karbon tersimpan tertinggi dihasilkan pada revegetasi tahun 2013 dengan total sebesar 81,61 ton/ha dan total kandungan karbon tersimpan sebesar 38,36 ton C/ha sedangkan biomasa total dan simpanan karbon di lahan revegetasi tahun 2018 adalah 33,23 ton/ha dan 15,62 ton C/ha dan biomasa total dan simpanan karbon di lahan revegetasi tahun 2016 adalah 75,48 ton/ha dan 35,48 ton C/ha. Kata kunci: biomassa, karbon, reklamasi, tambang, tumbuhan bawah, Plant inventories and carbon calculations are carried out to measure the success of post-mining land revegetation. Plant inventories and carbon calculations are carried out. This research aims to determine the diversity of understory plants and determine the potential for carbon deposits above ground and their relationship to differences in the age of revegetated land in 2018, 2016 and 2013. Plots were made using the sample plot method measuring 50 m x 50 m with a total of 3 plots. Each plot has 4 (subplots). Biomass measurements are carried out using non-destructive methods and using allometric formulas. The research results show that the diversity of the three revegetation ages is not much different. The highest total biomass and stored carbon content was produced in revegetation in 2013 with a total of 81,61 tons/ha and the total stored carbon content was 38,36 tons C/ha while the total biomass and carbon savings in revegetated land in 2018 was 33,23 tons/ha and 15,62 tons C/ha and total biomass and carbon storage in revegetated land in 2016 was 75,48 tons/ha and 35,48 tons C/ha. Keywords: biomass, carbon, mining, reclamation, undergrowth
Keyword: carbon, mining, reclamation, undergrowth

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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