Judul: Keanekaragaman Jenis Tumbuhan Bawah di Lahan Bekas Tambang Silika dan Kapur PT Holcim Indonesia Tbk., Jawa Barat
Abstrak: Kegiatan penambangan yang dilakukan secara terbuka menyebabkan kerusakan vegetasi penutup tanah, peningkatan laju erosi, penurunan produktifitas dan stabilitas lahan tidak produktif serta menurunkan kesuburan tanah. Kegiatan revegetasi membutuhkan waktu yang lama sehingga memerlukan penanaman tanaman penutup tanah (cover crop). Tujuan penanaman cover crop adalah untuk melindungi tanah dari ancaman erosi. Penelitian ini bertujuan untuk mengkaji komposisi jenis, keanekaragaman jenis dan potensi tumbuhan bawah untuk dijadikan sebagai cover crop. Komposisi tumbuhan bawah di lahan bekas tambang kapur lebih tinggi dibandingkan dengan lahan bekas tambang silika. Keragaman jenis (H’) pada masing – masing lokasi penelitian tergolong sedang. Kemerataan jenis (E) pada kedua lokasi penelitian tergolong tinggi. Kekayaan jenis (R1) pada kedua lokasi penelitian tergolong tinggi. Indeks dominansi (C) pada kedua lokasi penelitian tergolong rendah. Sifat tanah pada masing – masing lokasi tergolong kurang subur. Unsur hara yang terdapat pada kedua lokasi penelitian tergolong rendah
Keyword: cover crop, keanekaragaman jenis, sifat tanah, tumbuhan bawah

Judul: Keanekaragaman Tumbuhan Bawah pada Tegakan Sengon Buto (Enterolobium cylocarpum Griseb.) dan Trembesi (Samanea saman Merr.) di Lahan Pasca Tambang Batubara PT Kitadin Embalut, Kutai Kartanegara, Kalimantan Timur
Abstrak: Mining activities have a negative impact on the environment, as the Minister of Energy and Mineral Resources Regulation No. 18 of 2008 regarding the Mine Closure Plan in which requires mining companies to conduct reclamation activities on any pit mine. The research was carried out aimed to assess the composition and diversity of plant species, especially in the areas under coal mine revegetation after PT Kitadin Embalut, Kutai Kartanegara, East Kalimantan. This research conducted on the revegetation area PT Kitadin of sengon buto and trembesi stand planted on the year of 2006 for four month period of observation. Data collection methods used was step undergrowth vegetation, and data analysis is the INP of undergrowth species and analysis of plant diversity. Results showed that the total species found in both stand is 24 species from 20 families which scattered in the stands of sengon buto as many as 22 species from 19 families and the trembesi stands as many as 17 species from 13 families. The most dominated species in both stands is Paspalum conjugatum and Solanum torvum. Diversity level of undergrowth plant under stands of sengon buto and trembesi classified as medium. Richness level of undergrowth plant species is relatively low with a value of Richness (R1) on the stands of sengon buto is 2.56 and richness on the trembesi stands is 1.96. Evenness of undergrowth species under sengon buto and trembesi stands is categorized high because both the values level (E) > 0.6. The similarity index of undergrowth in sengon buto and trembesi stands can be considered as the same because the value of the IS> 75%.
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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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