RothC-26.3 is a model for the turnover of organic carbon in non-waterlogged topsoils that allows for the effects of soil type, temperature, moisture content and plant cover on the turnover process. It uses a monthly time step to calculate total organic carbon (t ha-1), microbial biomass carbon (t ha-1) and \Delta14C (from which the equivalent radiocarbon age of the soil can be calculated) on a years to centuries timescale. (Coleman and Jenkinson, 1999; Jenkinson et al. 1987; Jenkinson, 1990;Jenkinson et al. 1991; Jenkinson et al. 1992; Jenkinson and Coleman, 1994) It needs few inputs and those it needs are easily obtainable. It is an extension of the earlier model described by Jenkinson and Rayner (1977) and by Hart (1984).
A version replacing the monthly time steps by continuous processes has been published by Parshotam (1995). King et al (1997) have incorporated RothC into a much larger model for global C cycling. A comparative study of C turnover models, including RothC-26.3, has recently been published (Smith et al, 1997). RothC-26.3 is designed to run in two modes: forward in which known inputs are used to calculate changes in soil organic matter and inverse , when inputs are calculated from known changes in soil organic matter. RothC-26.3 was originally developed and parameterized to model the turnover of organic C in arable topsoils from the Rothamsted Long Term Field Experiments - hence the name. Later, it was extended to model turnover in grassland and in woodland and to operate in different soils and under different climates. It should be used cautiously on subsoils, soils developed on recent volcanic ash (but see Parshotam et al 1995, Tate et al 1996 and Saggar et al 1996), soils from the tundra and taiga and not at all on soils that are permanently waterlogged.
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