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: Subsidence and Percentage of CO2 Emission from the Decomposition to Subsidence of Peatland on Palm Oil Plantations
Abstrak: The drainage system on peatlands is aimed to eliminate limiting factors that can inhibit the growth of oil palm plantations. On the other side, peatland drainage practices will cause peat subsidence and it is associated with CO2 emissions from peatlands. Subsidence method is one of the methods commonly used in the approach to calculate CO2 emissions. The peat subsidence process consists of consolidation, compaction, and decomposition. Previous research resulted in emission data of 100 tons CO2/ha/year, of which 92% of the subsidence is considered as decomposed peat, and 8% is the components of compaction, soil respiration (autotroph and heterotroph). The percentage of decomposition to compaction-consolidation in the previous study was overestimated. The research was conducted on the oil palm plantation of Koto Gasib Village, Siak Regency, Riau Province. From January 2019 to January 2020. The study was carried out on oil palm plantation blocks on peatlands that have been controlled drained with a canal system to maintain water levels. Observational data were collected from 6 subsidence stick, 3 dipwells, 3 peat profiles, and LiCor 8100A automatic chamber. The observation interval for the observation of bulk density, subsidence, C-Organic and ash content every 3 months, while for the water level using the monthly average and every 30 minutes for CO2 flux. Peat analysis was conducted at the Laboratory of Chemistry and Soil Fertility, Department of Soil Science and Land Resources, IPB. The purpose of this study were to observe the rate of subsidence of tropical peatlands in oil palm plantations at various ages of oil palm plants, and to determine the percentage of decomposition of peat material from the subsidence rate. Subsidence was measured at adjacent oil palm planting blocks at 9, 12, and 17 years of age, with a peat thickness of about 5 m, and the land had been drained for 10, 13, and 18 years, respectively (one year prior to planting). Peat decomposition (heterotrophic respiration) is considered as actual CO2 emission compared to the calculated emission from subsidence which is considered as potential CO2 emission from the calculation of the subsidence method. Analysis of peat fiber at the research site generally shows that the deeper the surface of the peat, the higher the fiber volume with the average fiber at a depth of 0-10 cm 25.3% and classified into hemic peat. The peat density analysis using the kubiena box showed that the average density of peat at a depth of 0-20 cm in the three blocks observed was 0.134 g/cm3. Peat ash content shows accumulation on the peat surface as a result of the decomposition process of peat material, with an average of 5.83% and 2.31% at depths of 0-10 and 10-20 cm, respectively. Meanwhile, the organic C content of peat showed an average of 55.64% at a depth of 0-20 cm. The average subsidence rate for oil palm plantations on tropical peatlands 10-18 years after controlled drainage is 2.47 ±0.76 cm/year. Peatland subsidence is higher in older oil palms due to higher plant load and root density. There is a bouncing back phenomenon or an increase in the peat
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Judul: Grup dan Homomorfisma Grup pada Rubik Revenge
Abstrak: Rubik cube is a kind of puzzle game. A player must arrange rubik sides, which have been disordered, back to the position where every side has the same colour. This paper does not focus on the settlement solution, but instead on proving the existence of a group homomorphism between rubik movement group and S96 symmetric permutation group in rubik revenge. Firstly, it has been proved that rubik movement set is a group. Then, it also has been proved that the M set, which contains numeric labels of 1 until 96 in cubinos sides, is S96 symmetric permutation group.
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