Judul: Fluks CO2 dari Andosol pada Penggunaan Lahan Kebun Sayur dan Hutan di Kecamatan Cisarua Kabupaten Bogor
Abstrak: Recently, agricultural activities are considered as one source of greenhouse gas emissions (GHG). Researchs on GHG emission from agricultural land are mostly done on peat soils, while researchs on mineral soil are still limited. This research was aimed to find out and to compare CO2 flux from vegetable garden, forest, and bare land on Andosol, and to compare CO2 flux from peat soils with these of mineral soils. This research was carried out at tea plantation area of PT Sumber Sari Bumi Pakuan, Tugu Utara Village, Cisarua District, Bogor Regency (Puncak area). Gas samples were taken using a chamber method and CO2 measurement was done using a CO2 Analyzer. The results of CO2 flux measurement of each of the land uses on Andosol indicate that CO2 flux from vegetable garden and forest were almost similar, about 4.26 g C-CO2/m2/d and 4.28 g C-CO2/m2/d, while that of bare land showed smaller results, about 2.0 g CCO2/ m2/d. The results of analysis of soil respiration showed the same thing that is CO2 produced from soil of vegetable garden and forest is higher than that of bare land. These results are resembled by the results of the analysis of microbial populations in the soils of vegetable garden and forest that were higher than that of the bare land. That facts indicate that the amount of CO2 flux are more originated from respiration activity that depends on the plants condition and the microbes activity. CO2 flux from three landuses of Andosol ranging from 1.00 to 6.00 g C-CO2/m2/d (3.65-21.90 tons C-CO2/ha/y). The amount of CO2 flux on this range is comparable with that of the CO2 flux from peat soil. CO2 flux from Andosol (high organic matter soil) in this research was lower than that from Latosol (low organic matter soil), indicating that the soil organic matter not directly influence the CO2 flux from the soil. Differences of soil and environmental conditions that affects of plant respiration and soil microbial at the study site are supposed to be a major factor in influencing the difference of CO2 flux.
Keyword: agricultural land, CO2 flux, Andosol

Judul: Fluks CO2 dari Andosol pada Penggunaan Lahan Kebun Teh dan Tanah Bera di Desa Tugu Utara Kecamatan Cisarua Kabupaten Bogor
Abstrak: Global warming has became a critical environmental issue in the last years. This phenomenon is thought due to the increasing of greenhouse gases (GHG) concentration in the atmosphere. Carbon dioxide (CO2) is the major greenhouse gases generated by human activity that comes from the use fossil fuels for industrial activities, transportation, and household. Along with the increasing strength of is issue, agriculture is considered to be one of the sources of GHG emissions. There are already a lot of researches and publications regarding GHG emissions, particularly CO2 flux from agricultural land. There are a lot of informations on CO2 fluxes from peat land, but those from soil mineral is very limited. Therefore, a research needs to be done to measure flux of CO2 from mineral soil, especially that has high organic matter as in Andosol. The purposes of this study are to measure and compare CO2 flux of Andosol used for tea plantation and bare land, and to compare CO2 flux from mineral soils and peat soils. The method used for gas sampling is the closed chamber method and Infra- Red Gas Analyzer (IRGA) was used to measured CO2 concentration. The results showed that CO2 flux in the land used two lands on Andosol is about of 1.00 to 8.00 g C-CO2 m-2 day-1. Daily mean of CO2 fluxes were obtained from 25 weeks are 2.01 g C-CO2 m-2 day-1 (bare land) and 2.81 g C-CO2 m-2 day-1 (tea plantation). Mean daily CO2 flux of tea plantation was a higher than that of CO2 flux from bare land. These results are resembled by the data of microbial populations in the soil of tea plantation that was higher than that of the bare land. That facts indicate that the amount of CO2 flux are more originated from respiration activity that depend on the plant condition and the microbe activity. Andosol’s, Latosol’s and Peat soil’s CO2 fluxes in bare condition are almost the same. It shows that the CO2 flux from soil is not directly proportional to the content of soil organic matter.
Keyword: mineral soil, tea plantation, greenhouse gas, CO2 flux, Andosol

Judul: Dynamical System of Hepatitis B in Three Groups with Vaccination
Abstrak: The aim of this study is to modify the hepatitis B transmission model in three age groups involving vaccination from the model conducted by Zhoe and Zhang.The method used is to analyze the stability of the fixed point and its basic reproduction number (R_0). Performed stability analysis and numerical simulation to see population dynamics. Next, a sensitivity analysis of the parameters was carried out to see its effect on R_0. From the analysis obtained two fixed points, namely non-endemic and endemic fixed points. Non-endemic fixed points are locally asymptotically stable if R_0 <1 Meanwhile, the endemic fixed point is locally asymptotically stable if R_0 > 1. Hepatitis vaccination affects the number of susceptible population, because the more successful the vaccination, the smaller the number of susceptible populations so that the smaller the population will be infected.
Keyword: Dynamic, Hepatitis B, Vaccine, Mathematical model