Carbon sequestration under <i>Miscanthus</i> in sandy and loamy soils estimated by natural ¹³C abundance

Most studies of soil organic‐carbon (SOC) dynamics using 13 C natural abundance have been conducted with maize. Here, we present data about the sequestration of C derived from a perennial C 4 plant, Miscanthus × 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 0–10 cm. 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 g 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.