Judul: Keanekaragaman Lumut Epifit pada Gymnospermae di Kebun Raya Bogor
Abstrak: Researchs on diversity of epiphytic bryophytes are more common observed on Angiospermae than those on Gymnospermae. Bogor Botanical Garden (BBG) is an ex-situ conservation in which the sample plants are collected around the world for conservation purpose. Trees in the Botanical Garden provide substrats for epiphytic bryophytes. The temperature and humidity in the Botanical Gardens were the optimum range for the bryophyte growth. The aim of this research was to observe diversity of epiphytic bryophytes on Gymnospermae in BBG. The bryophyte samples were collected from Gymnosperm trees in Blok I which is Cycadaceae familly and those in Blok II which are the familly of Pinaceae, Araucariaceae, Gnetaceae, dan Podocarpaceae. Only the trees have ≥ 20 cm (dbh) of trunk base were sampled. Bryophytes were collected from the trunk base at 0-200 cm above the ground, at four cardinal direction (north, south, west, and east). In total 18 species of epiphytic bryophytes were found, included 12 genera and 7 families. The family which had the highest number of species was Lejeuneaceae. The most common species on Gymnosperm trees in the Botanical Garden were Lejeunea tuberculosa and Octoblepharum albidum. Both of them were found at 6 trees of 13 total tree samples. The species were found more frequently at west (2,1%) and north (1,8%) part than east and south part of the host trees. They more frequently inhabit the trunk base on 0-100 cm than 100-200 cm. Key words: Bogor Botanical Garden, diversity, epiphyte bryophyte, Gymnospermae.
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Judul: Lumut Terestrial dan Ganggang Asosiasinya di Kebun Raya Bogor
Abstrak: Bogor Botanical Garden is an ex-situ conservation which may serve as habitat for bryophyte. Terrestrial bryophyte usually grow on various substrates in shaded habitat or open habitat, such as roadside, along ditches, and rivers. One of the bryophytes benefit in ecosystem is to provide microhabitat for algae. This research was carried out to inventory the bryophyte species grow on terrestrial substrate, and to study their diversity and algal association. The bryophyte were collected on various terrestrial substrates (soil, root, and rock). Quadrates of 25 × 25 cm² were used to sample bryophytes along 30 m transect on three blocks which is dominated by plants with different family, i.e. Meliaceae, Myrtaceae, and Lauraceae to study the diversity. Bryophyte were also sampled used sub-quadrates of 2,5 × 2,5 cm² in the quadrate of 25 × 25 cm² to sample algae associated with bryophyte. Forty three species of terrestrial bryophytes were identified, including 33 species of mosses and 10 species of liverworts. The bryophytes diversity was significantly different when compared to different blocks (p < 0,05). The highest diversity of bryophyte was on block Meliaceae which were more intensively shaded than on any other block. The bryophytes composition was different inter block. Fissidens crassinervis var. laxus, Isopterygium bancanum, and Taxiphyllum cf. taxirameum were dominated on three blocks in Bogor Botanical Garden. These three bryophytes species are commonly grow on soil and roots. Thirteen morphospecies of algae were found in association with terrestrial bryophyte, i.e. Cyanophyta, Chrysophyta, and Chlorophyta.
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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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