Soils as Source and Sink of Environmental Carbon Dioxide
- Cite this paper as:
- Lal R. (2010) Soils as Source and Sink of Environmental Carbon Dioxide. In: Xu J., Huang P.M. (eds) Molecular Environmental Soil Science at the Interfaces in the Earth’s Critical Zone. Springer, Berlin, Heidelberg
World soils contain 2500 Pg C to 1-m depth, comprising of 1500 Pg of soil organic C (SOC) and 950 Pg of soil inorganic C (SIC) (Houghton, 2007;Lal, 2004). Therefore, the soil C pool is 3.1 times more C than the atmospheric pool (800 Pg and increasing at the rate of 4.1 Pg C·yr−1) and 4.0 times the biotic pool (620 Pg and decreasing at the rate of 1.6 Pg C·yr−1). The current global C budget comprises anthropogenic emissions of 8.0 Pg C·yr−1 from fossil fuel combustion and cement manufacture, and 1.6 Pg C·yr−1 from deforestation, biomass burning and soil cultivation. Of the total emission of 11.5 Gt C E (including CO2, CH4 and N2O) in 2000, 14% (1.6 Pg) were those due to agricultural activities and 18% (2.1 Pg) from land use conversion. Thus, land use and agriculture contribute about one-third (32%) of total anthropogenic emissions. Confirmed sinks include atmospheric absorption of 4.1 Pg C·yr−1, oceanic uptake of 2.3 Pg C·yr−1, and a land sink of about 1.5 Pg C·yr−1 (WMO, 2008). Thus, there is an unknown terrestrial sink of about 1.7 Pg C·yr−1.