Judul: CO2 Flux and Decomposition Rate of Dead Roots of Oil  Palm at Different Water Content
Abstrak: Pengembangan lahan gambut menjadi lahan perkebunan kelapa sawit banyak dilaporkan berpotensi meningkatkan emisi Gas Rumah Kaca (GRK). Fluks CO2 yang selama ini diukur umumnya mencakup keseluruhan dari total respirasi heterotrof, sedangkan kajian terkait fluks CO2 dari bahan organik lain seperti akar mati kelapa sawit masih terbatas. Akar mati disimulasikan pada beberapa % kadar air berbeda dengan mengikuti kondisi kadar air di lahan gambut, sehingga dapat merepresentasikan pada kadar air gambut dalam mempengaruhi laju dekomposisi akar mati. Penelitian ini diharapkan dapat menunjukkan kisaran kontribusi akar mati kelapa sawit dalam menyumbang fluks CO2 dari respirasi heterotrof di lahan gambut, sehingga penetapan fluks CO2 dari respirasi heterotrof tidak overestimate. Pengukuran fluks CO2 menggunakan alat IRGA (Infra Red Gass Analyzer) Li COR 830 dengan metode sungkup tertutup (clossed chamber). Akar mati dikering udarakan dan dibersihkan dari sisa-sisa partikel gambut yang menempel di permukaan akar, lalu dilakukan pemotongan dengan ukuran 2 cm. Perlakuan pada penelitian ini terdiri dari perlakuan kontrol dan perlakuan kadar air 100%, 150%, 300%, dan 450% dengan lima ulangan untuk masing-masing perlakuan, sehingga terdapat 25 satuan percobaan. Masing-masing perlakuan dimasukan ke dalam chamber dengan ukuran diameter 11 cm dan tinggi 14 cm. Kadar air berpengaruh terhadap proses dekomposisi akar mati kelapa sawit dan pelepasan CO2. Perlakuan kontrol memiliki nilai fluks CO2 dan laju dekomposisi yang lebih rendah dibandingkan perlakuan kadar air. Nilai fluks CO2 terendah pada perlakuan kontrol dan tertinggi pada kadar air 100%. Dinamika laju dekomposisi pada nilai C/N tertinggi yaitu pada perlakuan kontrol dan terendah pada perlakuan kadar air 150% serta kehilangan bobot tertinggi pada perlakuan kadar air 100% dan terendah pada perlakuan kontrol. Meskipun nilai C/N masih tergolong pada kategori tinggi, penurunan tersebut mengindikasikan adanya laju dekomposisi yang terjadi selama masa inkubasi. Semakin lama masa inkubasi, semakin meningkatkan laju dekomposisi yang dilihat dari penurunan C/N dan kehilangan bobot yang meningkat akibat proses dekomposisi., The development of peatlands into oil palm plantations is widely reported to increase greenhouse gas (GHG) emissions. CO2 flux that has been measured generally covers the entirety of total heterotrophic respiration. In contrast, studies related to CO2 flux from other organic materials such as dead roots of oil palm are still limited. Dead roots are simulated at several % of water content differently by following the water content conditions in peatlands to represent the content of peat water in influencing the decomposition rate of dead roots. This research is expected to show the range of contributions of dead roots of oil palm in contributing CO2 flux from heterotrophic respiration in peatlands so that the determination of CO2 flux from heterotrophic respiration is more reliable. CO2 flux was measured by IRGA (Infra Red Gass Analyzer) Li-COR 830 tool with a closed chamber method. Dead roots are air-dried and cleaned from the remains of peat particles attached to the surface of the roots, then cut with a size of 2 cm. The treatment in this study has consisted of control treatment and water content treatment of 100%, 150%, 300%, and 450% with five repeats for each treatment, so there were 25 experimental units. Each treatment is inserted into a chamber
Keyword: CO2 emission, peat, decomposition, C/N, lose weight

Judul: Dynamics of CO2 Fluxes from Oil Palm Plantations on Peatland
Abstrak: The use of peatlands for plantations has received international attention related to environmental issues, namely the release of carbon suspected to be in large quantities. The release of carbon in the form of CO2 from peatlands is also related with increasing global temperatures. The release of CO2 from the soil surface is also known as CO2 flux. The CO2 flux from oil palm plantations has so far been estimated from the results of CO2 flux measurements in the inter row, but not much from the harvesting path. In the harvesting path, the cover plants were less and more exposed when compared to inter row. This condition allows for different environmental conditions that can affect the CO2 flux. For this reason, it is also necessary to measure CO2 flux at the harvesting path to get a more precise value of CO2 flux in estimating CO2 flux from oil palm plantations. CO2 flux can be partitioned into fluxes from oil palm root respiration, litter decomposition, and peat material decomposition.Measurement of CO2 flux to separate the source of flux from oil palm root respiration and peat material decomposition is generally done by comparing the flux produced at a distance of 3.5 – 4.5 m from the oil palm trunk by plot trenching or root cutting method. At this distance, it is still possible to contribute plant root respiration to flux. Cutting roots can minimize the effect of root respiration. However, dead roots are a source of new organic matter for microbial activity, thereby contributing to the measured CO2 flux. CO2 flux measurements carried out at sites far from oil palm can minimize the influence of the contribution of plant roots to flux so that more precise data on the contribution of root respiration, litter and peat material decomposition to flux obtained. Thus, the aim of this study was to determine the spatial and temporal dynamics of CO2 flux, the contribution of root respiration and litter decomposition to flux, and their relationship to environmental factors in oil palm plantations on peatlands. The research was conducted in Pangkalan Pisang Village, Koto Gasib District, Siak Regency, Riau Province. Measurement of CO2 flux was carried out in oil palm plantations with a plant age of 14 years and bushland dominated by ferns (Nephrolepis sp). The location of the bushland in this study is still in oil palm plantations. Measurement of CO2 flux using an infrared gas analyzer (IRGA) was carried out in harvesting path, inter row and bushland. Estimation of CO2 flux from oil palm plantations is based on the value of CO2 flux from harvesting path and inter row that contain litter on the soil surface. Flux measurements without litter were also carried out to estimate the litter contribution to CO2 flux. Flux measurements were repeated every three to four days from May to September 2019. Results showed the dynamics of the CO2 fluxes spatially and temporally. The difference in flux values that occur indicates that although on the same expanse of land with plant age, air humidity, air temperature, soil temperature, and groundwater table depth are relatively
Keyword: litter decomposition, peat material, root respiration

Judul: Query Expansion based on Bilingual Dictionary Using Conditional Probability
Abstrak: Query expansion is a technique that can be used to bridge vocabulary gaps between queries and documents in the collection. With query expansion, user will be helped to formulate queries well so that user will optimize the search result. In this study, the expansion term was resulted from the translation of bilingual dictionary. Subsequently, several terms of expansion were elected based on the closeness of its relationship with the original query. This research showed that conditional probability can be used to select expansion term in bilingual translation method query expansion. The result of 1000 documents was more than 97% relevan document can be retrieved by this system. The more expansion term used, the larger number relevan document was retrieved.
Keyword: