mortiz085

Methane (CH4) and carbon dioxide (CO2) are the end products of carbon decomposition in rice fields and other wetlands. Methane, a major greenhouse gas, is the terminal step of the anaerobic breakdown of organic matter in wetland soils. It is exclusively produced by methanogenic bacteria that can metabolize only in the absence of free oxygen and at redox potentials below -150 mV (Neue et al. 1997). According to the above-cited paper by Dr.H.U. Neue (former Head of the Soils Department at IRRI and later Professor of Soil Chemistry at the University of Halle-Wittenberg, Germany) one of the pioneers in methane research in rice fields, methane is largely produced by transmethylation of acetic acid and to some extent, by the reduction of carbon dioxide in wetland soils. The rate and pattern of organic matter addition and decomposition also contribute to the rate and pattern of methane production. In rice field, methane production generally increases during the cropping season. Easily degrad...

The missing carbon sink is the large amount of unidentified carbon sink in the global carbon budget. According to the Woods Hole Research Center (2007) the average annual carbon emissions amount to 8.5 Pg (1 Pg or petagram is equal to 1 billion metric tonnes) comprising of 6.3 Pg from combustion of fossil fuels and 2.2 Pg from changes in land use. This is greater than the sum of the annual accumulation of carbon in the atmosphere (3.2 Pg) plus the annual uptake by the oceans (2.4 Pg) which is only 5.6 Pg. The difference of 2.9 Pg (i.e. 8.5-5.6=2.9) is unknown carbon sink required to balance the carbon budget. Scientists have been searching for this big amount of unknown carbon sink during the last two decades. It was first thought to be located in the ocean considering that it occupies 70% of the earth’s surface. However, most scientists consider that the ocean sink is not big enough to account for the missing carbon (Xie et al., 2009). The next possible location is the world’s forest...