Judul: Karakteristik tanah pada lahan bekas tambang yang ditanami rumput signal (Brachiaria decumbens Stapf) di PT. International Nickel Indonesia Sorowako Sulawesi Selatan
Abstrak: PT. INCO merupakan perusahaan tambang nikel yang berlokasi di Sorowako, Sulawesi Selatan. Kegiatan penambangan dilakukan di darat dengan menerapkan teknik penambangan terbuka (open pit mining). Kondisi lahan-lahan bekas tambang ini umumnya terbuka tanpa vegetasi, tidak subur, dan berlereng sehingga memerlukan reklamasi yang tepat. Dalam tahapan revegetasi untuk mengurangi laju erosi dilakukan penanaman tanaman penutup tanah. Jenis tanaman penutup tanah yang digunakan di lokasi ini adalah Brachiaria decumbens Stapf (rumput signal). Namun, karena pertumbuhannya yang cepat dan sukar dikendalikan rumput ini mengganggu pertumbuhan tanaman pionir. Pengendalian total dengan penyemprotan herbisida terhadap rumput signal diharapkan dapat menambah bahan organik tanah.
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Judul: Evaluasi Tingkat Keberhasilan Revegetasi Lahan Bekas Tambang Nikel Di Pt Inco Tbk. Sorowako, Sulawesi Selatan
Abstrak: PT INCO has made a borrow and use agreement with the government to do mining activity in forest area. This mining activity has caused severe damage to the forest and the land. With full awareness and to fulfill obligation in borrow and use agreement, PT INCO has done rehabilitation to severely damage forest and lands due to its mining activity. An evaluation is needed to measure the succession rate of rehabilitation effort that has been done by PT INCO. This evaluation put an emphasis on vegetational and biological aspect, enabling to see how far the revegetation activity able to fulfill restoration purpose as mention in Permenhut Nomor 146/Kpts-II/1999 and to restore functions of a forest. Object of this research is forest stand resulted from revegetation planted in 1999-2007, 1985 and 1996. Some of the equipments been used in this activity are brunton compass, measuring band, Sunto clinometer, spherical densiometer, plastic rope. Vegetational analysis done by using 17,8 m diameter circle plot. For each planting year make 2-3 plots with range 50 - 100 meter between each plot, for some cases such as limited land one plot is sufficient enough. In it observation made to plant growth factor such as plant height, plant diameter, root development and crown covering. Another parameter that also observed are local species existances and wildlife presence. Growth percentage in revegetation area range from 95% to 100%. Plant composition are pioneer species as Sengon (Paraserianthes falcataria), Eukaliptus (Eucalytus eurograndis), Sengon Buto (Enterolobium macrocarpum)and local species as Trema (Melochia umbellata), Sandro (Sandoricum kacappeae) dan Uru (Elmerelia sp). This mean it is suitable with goverment rule. Root development, growth, litter decomposition, erotion and crown covering has shown improvement according to succession concept. Same thing happen to wildlife, introduction has happened to revegetation lands. Revegetation at PT INCO in some aspects has fulfill goverment´s criteria and indicator but this revegetation has not reform original forest structure and function as protected forest.
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Judul: Approximation of the Median of Poisson Distribution Using the Relation of Poisson-Gamma Distribution
Abstrak: A major drawback of median is that median cannot usually be defined in closed form, even in the cases where their distribution functions are known. This study gives an approximation of the closed form for the median of the Poisson distribution by using the relation of Poisson-Gamma distribution. The approximation uses elementary techniques based on the monotonicity of certain sequences involving tail probabilities of the Poisson distribution and the Central Limit Theorem. Furthermore, a closed form expression for the mean absolute deviation 􀜧|􀜰􀰒 􀵆 􀜯􀝁􀝀􁈺􀜰􀰒􁈻| is also studied. The median is relevant because of the fact that it minimizes the mean absolute deviation of a Poisson random variable (􀜰􀰒􁈻 by considering median as central tendency.
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