Judul: Decomposition of Agathis dammara (Lamb.) Leaves,  Soil Fauna Abundance, and Soil Characteristics in Gunung Walat University  Forest
Abstrak: Serasah adalah sumber nutrisi bagi unsur biotik di sekitarnya. Fauna tanah berperan dalam dekomposisi serasah, menguraikan unsur hara, dan memengaruhi siklus nutrisi. Penelitian ini bertujuan menganalisis hubungan antara faktor edafis dan klimatis terhadap laju dekomposisi daun serta mengidentifikasi fauna tanah di bawah tegakan Agathis dammara (Lamb.). Pengambilan sampel dilakukan pada petak contoh 20 m x 20 m secara acak dengan sub-plot systematic sampling 0,5 m x 0,5 m. Hasil analisis menunjukkan laju dekomposisi pada minggu ke 4, 8, dan 12 secara berturut-turut sebesar 0,92 g/minggu, 1,51 g/minggu, dan 1,29 g/minggu. Korelasi antara laju dekomposisi dengan faktor edafis seperti pH, suhu, kelembapan, respirasi, bahan organik, dan c-organik menunjukkan korelasi positif. Faktor klimatis juga berpengaruh: kelembapan udara dan suhu udara memiliki korelasi positif, sedangkan intensitas cahaya menunjukkan nilai negatif. Indeks keanekaragaman fauna tanah berkisar antara 0,30-1,90; nilai kemerataan berkisar antara 0,15-0,82; dan nilai kekayaan berkisar antara 0,63-2,10; yang menunjukkan indeks keanekaragaman yang tergolong rendah hingga sedang.
Keyword: soil fauna

Judul: Decomposition Rate and Site Characteristics in the Agroforestry System at Mount Kendeng Resort, Mount Halimun Salak National Park.
Abstrak: Leaf litter has a positive influence on the physical and chemical properties of soil through the provision of organic matter on the soil surface. This study aimed to measure the decomposition rate of leaf litter, and analyze the relationship between site characteristics and environmental conditions on the decomposition rate in agroforestry systems areas. Vegetation analysis was carried out on 50 m x 50 m sample plots totalling 14 plots. In addition, decomposition rate analysis, site characteristics, climate, and correlation tests were carried out. The dominant tree species in agroforestry systems areas was Agathis dammara. The highest and lowest decomposition rates in agroforestry systems areas at Gunung Kendeng Resort were 0.57 g/day and 0.33 g/day, respectively. The correlation between decomposition rate and edaphic factors that had a positive correlation were pH, soil organic matter, organic carbon, and porosity, while soil temperature, soil respiration, and bulk density had a negative correlation. The correlation between decomposition rate and climatic factors that had a positive correlation was moisture, while air temperature and light intensity had a negative correlation., Serasah memiliki pengaruh yang positif terhadap sifat fisik dan kimia tanah melalui penyediaan bahan organik di permukaan tanah. Penelitian ini bertujuan untuk mengukur laju dekomposisi serasah daun, dan menganalisis hubungan karakteristik tapak dan kondisi lingkungan terhadap laju dekomposisi pada areal sistem agroforestri. Analisis vegetasi dilakukan pada plot contoh 50 m×50 m sebanyak 14 plot. Selain itu, dilakukan analisis laju dekomposisi, karakteristik tapak, dan klimatis, serta uji korelasi. Jenis pohon yang mendominasi pada areal sistem agroforestri adalah Agathis dammara. Laju dekomposisi tertinggi dan terendah pada areal dengan sistem agroforestri di Resort Gunung Kendeng secara berturut-turut sebesar 0,57 g/hari dan 0,33 g/hari. Hubungan korelasi laju dekomposisi dengan faktor edafis yang memiliki korelasi positif adalah pH, bahan organik tanah, C-Organik, dan porositas, sedangkan suhu tanah, respirasi tanah, dan bulk density memiliki korelasi negatif. Hubungan korelasi laju dekomposisi dengan faktor klimatis yang memiliki korelasi positif adalah kelembapan, sedangkan suhu udara dan intensitas cahaya memiliki korelasi negatif.
Keyword: agroforestri, dekomposisi, karakteristik edafis, karakteristik klimatis, serasah

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