Judul: Silvicultrual practices and growth of jabon tree (Anthocephalus cadamba Miq) in Community Forest, West Java, Indonesia
Abstrak: Jabon (Anthocephalus cadamba Miq.) is a native species in Indonesia. This fast growing tree is now preferred for the local community to plant because of its good adaptability and economic profitability. However, the information of this tree and silvicultural practices is still lacking. Therefore, there are three main objectives of this research: 1) to document the existing silvicultural practices of jabon implemented by local communities in West Java. 2) to investigate tree growth performance among different sites in West Java. 3) to examine the linkage of silvicultural practices and soil fertility for stand quality. This research covered following aspects; stand inventory, soil sampling and interview with local communities who planted jabon in the districts of Bogor, Sukabumi, Sumedang and Purwakarta. With 0.02 or 0.04 ha size sample plots, a stand inventory has been conducted and the diameter and height are measured. In addition, pest investigation also has been carried out at same sample plots. In addition, soil sampling and interview have done to collect site information and silvicultural practices in each site. After collecting various data from jabon plantation in West Java, those data are analyzed in forms of tabulation and regression graph. According to the results of the interview, most jabon plantations are owned by outsiders from Jakarta or other cities. There are three types of management: partnership, hiring employees and direct management. There are only a few practitioners have participated in silvicultural training. In spite of the absence of systematic silvicultural training, all practitioners have implemented basic silvicultural practices: land preparation and planting, fertilizing, maintenance and pest and disease control. Moreover, most of sites in same village have same or similar silvicultural practices because usually only one manager or farmer maintains all plantations. After an inventory of jabon plantations in West Java, there are totally 56 plots have been inventoried in 20 sites. The age of jabon tree ranges from 0.5-year to 3.5-year because jabon tree has been introduced in Java since 2008. The mean diameter ranges from 2.45 cm to 14.57 cm with maximum 29.3 cm and the mean height of 1.29 m to 12.62 m with maximum 18.68m in Situgede. As a result of regression modeling with dominant height, one Chapman model has been selected to calculate site index curve.: Hd 􀵌 10. 6982􁈺1 􀵆 exp􁈺􀵆0.8915t􁈻􁈻􀀀.􀀀􀀀􀀀􀀀 with 0.6513 R-square value. This curve helps to divide 20 sites into three categories: good, medium and poor. Based on analysis, there are two good sites, twelve medium and six poor sites. There are three DBH-age equations can be estimated based on site classifications. As a result of comparison between good and poor sites, it seems that site conditions and soil fertility have a more significant impact on growth of jabon than silvicultrual practices like fertilization and maintenance.
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Judul: Silvicultrual Practices and Growth of Jabon Tree (Anthocephalus cadamba Miq) in Community Forest, West Java, Indonesia
Abstrak: Jabon (Anthocephalus cadamba Miq.) merupakan jenis pohon cepat tumbuh asli Indonesia yang disukai oleh masyarakat karena adaptabilitas dan nilai ekonomi tinggi. Informasi mengenai pohon dan praktek silvikultur masih terbatas, Oleh karena itu, tujuan dari penelitian ini adalah: 1) mengumpulkan informasi mengenai praktek silvikultur yang telah dilaksanakan oleh masyarakat lokal di Jawa Barat 2) menginvestigasi performa pertumbuhan pada lokasi penanaman yang berbeda di Jawa Barat 3) menguji hubungan praktek silvikultur dengan kesuburan tanah untuk mengetahui kualitas tegakan. Aspek yang diteliti meliputi inventarisasi tegakan, pengujian contoh tanah, dan wawancara dengan masyarakat penanam jabon di wilayah Bogor, Sukabumi, Sumedang dan Purwakarta. Sebanyak 56 plot contoh dengan ukuran 0.02 atau 0.04 ha dibuat di 20 lokasi untuk melakukan pengukuran tinggi dan diameter pohon, dan serangan hama. Selain tinggi dan diameter, pada plot contoh juga diamati kerusakan pohon akibat hama. Data yang diperoleh dari lapangan, kemudian dianalisis dan disajikan dalam bentuk tabulasi dan grafik regresi. Berdasarkan dari hasil wawancara, sebagaian besar pemilik modal penanaman jabon berasal dari luar kota. Terdapat tiga tipe dari sistem menejemen yang dilakukan yaitu: kerjasama, menggaji karyawan, dan melakukan menejemen langsung yang dilakukan oleh pemilik modal. Berdasarkan informasi yang diperoleh, diketahui masih sedikit pengelola yang telah mengikuti pelatihan teknik selvikultur jabon Namun demikian semua pengelola telah menerapkan teknik dasar silvikultur seperti persiapan lahan, penanaman, pemupukan, serta pengendalian gulma, hama dan penyakit. Dari hasil inventarisasi diketahui pohon jabon di lapangan berusia antara 0,5 sampai 3.5 tahun, karena pohon jabon baru diperkenalkan sejak tahun 2008. Interval diameter rata-rata berkisar 2.45 cm sampai 14.57 cm, dengan nilai terbesar 29.3 cm dan tinggi rata-rata berkisar antara 1.29 m sampai dengan 12.62 m dengan tinggi maksimal sebesar 18.68 m di lokasi Situgede Bogor. Model Chapman digunakan untuk menghitung kurva index tempat tumbuh. Berdasarkan model regresi dari peninggi tegakan, nilai kurva index tempat tumbuh: Hd = 10. 6982(1 − exp(−0.8915t)). dengan nilai R-Square 0.6513. Nilai dari kurva ini, membagi 20 lokasi menjadi 3 katagori yaitu baik (2), sedang (12), dan buruk (6). Terdapat tiga persamaan antara umur dan diameter (DBH), yang dapat diperkirakan berdasarkan klasifikasi dari lokasi. Hasil dari perbandingan antara lokasi baik dan buruk, tampak bahwa kondisi lokasi dan kesuburan tanah lebih memberikan pengaruh yang nyata terhadap pertumbuhan jabon, dibanding dengan praktek silvikultur seperti pemupukan dan pemeliharaan.
Keyword: Anthocephalus cadamba Miq, Community Forest, Silvicultural practices, Site Index Curve

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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