Carbon sequestration under Miscanthus in sandy and loamy soils estimated by natural 13C abundance

Most studies of soil organic-carbon (SOC) dynamics using C-13 natural abundance have been conducted with maize. Here, we present data about the sequestration of C derived from a perennial C-4 plant, Miscanthus x giganteus (Greef et Deu.) grown on loamy and sandy soils for 9 and 12 y, respectively. We expected a higher contribution of Miscanthus-derived C to SOC formation compared to maize because of (1) higher net biomass production by Miscanthus, (2) lower shoot-to-root ratio, (3) deeper roots, and (4) the absence of plowing. In both soils, there was a significant contribution of Miscanthus-derived C down to 1 m soil depth. The maximal contents of 3.0 g C-4-C (kg soil)(-1) and 2.4 g C-4-C (kg soil)(-1) for loamy and sandy soil, respectively, were observed for the upper 0-10 cm layer. The decline in the amount of Miscanthus-derived C with soil depth was significant for both soils, but without significant differences between the differently textured soils except the depth of 0-10cm. The total SOC was similar under Miscanthus and under reference grassland in the sandy soil (both 6.4 kg C m(-2) down to 1 m soil depth). Amounts of SOC were slightly higher under grassland at the loamy site (12.1 kg C m(-2) compared with 11.2 kg C m(-2)). So, C accumulation under Miscanthus was similar to that under perennial grasses. After 9 and 12 y, respectively, the yearly incorporation of Miscanthus-C in SOC of the upper 0-30 cm was 0.23 9 C-4-C (kg soil)(-1) y(-1) in the loamy and 0.11 g C-4-C (kg soil)(-1) y(-1) in the sandy soil. This C-4-C incorporation in loamy soil under Miscanthus was 1.6-1.8 times higher than results reported for maize C-4-C incorporation in SOC grown under similar climatic conditions. In the sandy soil, the C-4-C incorporation under Miscanthus was nearly the same as under maize. The fraction of 22% of the Miscanthus residues remaining in SOC was similar to that one of maize residues in loamy soil. In sandy soil, only a small fraction of 9% of the Miscanthus residues was incorporated in SOC.