ABSTRACT
This chapter reviews and discusses some current definitions, proposes an alternative one, and draws attention to some necessary cautions when referring to soil carbon sequestration. Intensive speculations are being made about a future Carbon (C) market. C sequestration is more effective when the mean residence time of new C stored is long. It is, thus, absolutely necessary to evaluate the different C pools and to have an estimate of their respective turnover time. Several issues with regards to time and space scales must be addressed. The desirable time scale has to be sufficient to cover the entire vegetation successions and husbandries for a specific agroecosystem, and must be considered on multi-decadal scales. The major disadvantage of the diachronic approach is that one must wait and measure over long periods of time before being able to evaluate the quantity of C sequestered.
