Carbon storage in soils of Southeastern Nigeria under different management practices

The highest carbon stocks, 7906-9510 gC m-2, were found at the sites representing natural forest, artificial forest and artificial grassland ecosystems. Continuously cropped and conventionally tilled soils had about 70% lower carbon stock (1978-2822 gC m-2). Thus, the soil carbon stock in a 45-year old Gmelina forest was 8987 gC m-2, whereas the parts of this forest, that were cleared and continuously cultivated for 15 years, had 75% lower carbon stock (1978 gC m-2). The carbon stock of continuously cropped and conventionally tilled soils was also 25% lower than the carbon stock of the soil cultivated by use of conservation tillage.Introducing conservation tillage practices may reduce the loss of soil carbon stocks associated with land conversion. However, the positive effect of conservation tillage is not comparable to the negative effect of land conversion, and may not result in significant accumulation of carbon in southeastern Nigeria soils.Soil organic carbon is a large and active pool, containing roughly twice as much carbon as the atmosphere and 2.5 times as much as the biota. Carbon sequestration is the facilitated redistribution of carbon from the air to other pools. This would reduce the rate of atmospheric CO2 increase, thereby mitigating global warming [1,2].The amount of carbon sequestered at a site reflects the long-term balance between influx and efflux of carbon. Recent concerns with rising atmospheric levels of CO2 have stimulated interest in C flow in terrestrial ecosystems and the latter's potential for increased soil carbon sequestration [3]. Carbon enters the soil as roots, litter, harvest residues, and animal manure. It is stored primarily as soil organic matter (SOM). The density (w/v) of carbon is highest near the surface, but SOM decomposes rapidly, releasing CO2 to the atmosphere. Some carbon becomes stabilized, especially in the lower part of the profile. However, in many areas, agricultural and other land use activities have upset the nat