Judul: Pertumbuhan Kayu Putih (Melaleuca leucadendron Linn.) dan Longkida (Nauclea orientalis Linn.) pada Kondisi Tergenang Air Asam Tambang
Abstrak: Most of the coal mining operations in Indonesia use open mining systems that could expose sulfide minerals, so cause Acid Mine Drainage (AMD) surface if oxidized with O2 and met H2O. The problems experienced by each company which is active in mining coal, including PT Mandiri Intiperkasa. Handling of AMD that has been done is the provision of lime to neutralize the pH before being released into public waters. However, this can only be done if the company is still actively operating. Therefore, the AMD also need to be addressed passively, which will continue to work even though the company has stopped operating. Handling AMD passively conducted with make a pond sedimentation (settling pond) which is usually planted with grass tifa (Typha angustifolia). This technique is also known as wetland. Although this technique is capable of resolving the problem AMD, but can cause land becomes unproductive because overgrown grass species only. Therefore, it is necessary to add commercial tree types that can survive and grow well in a pool of AMD condition, so that someday can provide the added value of wood and non-wood. The selection of tree species based on the results of previous research that states that the kayu putih (Melaleuca leucadendron) and longkida (Nauclea orientalis) is able to survive in conditions of puddle water. The both types were also selected in this research, but the water used for flooding is the AMD. This research aims to know the viability and growth of kayu putih and longkida in a puddle of AMD, and the influence of both types are on the increase in pH AMD. The research conducted in the nursery PT Mandiri Intiperkasa, East Kalimantan in May–July 2011. The research conducted using Completely Randomized Design (CRD) by treatment with a combination of plants, namely tifa and kayu putih, tifa and longkida, as well as the tifa alone. Each experiment repeated three times, so there are nine units of the experiment. The observations of seedlings conducted during the four-week with the observed variables are the diameter and height growth, the pH of the AMD, plant dry weight, root shoot ratio, analysis of the vegetative organs of plants, and sludge analysis. The acquisition of data processed using Microsoft Excel and Minitab 14. The research states that each unit experiment increase in pH AMD, with first pH of 2.8 and at the end of the observation of up to 6.6. However, the increase in pH of the AMD was not influenced by the type of plant. The both types of trees, both kayu putih and longkida able to survive and to grow well for four weeks on puddle AMD condition.
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Judul: Evaluation of the Growth of Kayu Putih (Melaleuca cajuputi) Reclamation Results on PT Bukit Asam Post-mining Land, South Sumatera
Abstrak: Penambangan batu bara dengan metode open pit mining menyebabkan gangguan terhadap lingkungan sehingga reklamasi dan revegetasi perlu dilakukan. Revegetasi di PT Bukit Asam dilakukan dengan menggunakan tanaman lokal jenis kayu putih yang ditanam tahun 2016 – 2021. Tujuan penelitian yaitu mengevaluasi pertumbuhan kayu putih pada tahun tanam 2016 – 2021 serta menentukan status keberhasilan reklamasi berdasarkan daya hidup dan tutupan tajuk di lahan pascatambang PT Bukit Asam. Metode pengumpulan data pertumbuhan tegakan kayu putih dilakukan dengan purposive sampling pada petak ukur berukuran 40 m x 25 m. Intensitas sampling yang digunakan sebesar 5% dari lahan pascatambang kayu putih seluas 24 ha. Hasil penelitian menunjukkan bahwa tinggi, diameter batang, tebal tajuk, diameter tajuk, dan luas tajuk kayu putih pada tahun tanam 2016 memiliki pertumbuhan paling besar, sedangkan pada tahun tanam 2021 memiliki pertumbuhan paling rendah. Reklamasi lahan pascatambang pada tahap revegetasi telah mencapai nilai persentase hidup kayu putih > 80%, tetapi pada tahap penyelesaian akhir reklamasi belum berhasil dilakukan karena persentase tutupan tajuk kayu putih < 80%., Coal mining using the open pit mining method causes environmental disturbances, so reclamation and revegetation need to be carried out. At PT Bukit Asam, revegetation is carried out using local tree species, specifically kayu putih, planted between 2016 – 2021. The research aims to evaluate the growth of kayu putih during the period from 2016 – 2021 and determine the success status of reclamation based on tree survival rate and canopy cover in PT Bukit Asam’s post-mining land. Data collection for kayu putih tree growth was conducted using purposive sampling in sample plots measuring 40 m x 25 m. A sampling intensity of 5% was applied to the 24 ha post-mining reclamation area for kayu putih. Research results indicate that tree height, stem diameter, canopy thickness, canopy diameter, and canopy area of kayu putih showed the highest growth in the 2016 planting year, while the lowest growth occurred in the 2021 planting year. Although reclamation of post-mining land during the revegetation phase has achieved a survival rate of kayu putih > 80%, the final completion stage of reclamation has not been successful due to a canopy cover percentage < 80%.
Keyword: Canopy cover, Post-mining land, Survival rate, Tree growth

Judul: Metrik Einstein (Anti-) Self-Dual Berdimensi Empat dengan Metode Cartan
Abstrak: Gravitational field equation can be formulated in differential forms (differential geometry), which describes gravity as a manifestation of the curvature of space-time. Curvature of space-time is characterized by a metric that satisfies the gravitational field equation. With differential forms it can be formulated the (anti-) self-dual Einstein equation, which is a modification of the Cartan structure in (anti-) self-dual basis. Calculation of (anti-) self-dual metric with (anti-) self-dual Einstein equation is simpler than the calculation using Christoffel symbols.
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