Differences in soil aggregate, microbial biomass carbon concentration, and soil carbon between Pinus rigida and Larix kaempferi plantations in Yangpyeong, central Korea

This study was conducted to examine the soil aggregate distributions and their relationship with microbial biomass carbon (C) concentration and soil C in Pinus rigida and Larix kaempferi plantations. Soil samples of 0–10 cm, 10–20 cm, and 20–30 cm depth were collected and the microbial biomass C concentration was measured. The soils were then classified into four aggregate size classes by wet-sieving procedure [large macroaggregate (>2000 μm), small macroaggregate (250–2000 μm), microaggregate (53–250 μm), and silt-plus-clay (<53 μm)] and the C content of each aggregate size class was analyzed. The L. kaempferi plantation contained more macroaggregate over 250 μm than the P. rigida plantation did. The mean weight diameter (MWD) of the soil aggregate up to 30 cm depth was 1.26 mm and 1.45 mm in the P. rigida and L. kaempferi plantations, respectively, and it decreased with soil depth. The microbial biomass C concentration up to 30 cm depth was 510 μg C g soil⁻¹ for the P. rigida plantation and 764μg C g soil⁻¹ for the L. kaempferi plantation, and it was greatest in the surface soil in both plantations. The mean soil C concentration up to 30 cm depth was 2.00% for the P. rigida plantation and 2.88% for the L. kaempferi plantation. In both plantations, the soil C concentration was higher in the surface soil than in the deep soil. However, there was no significant difference of C concentration among the soil aggregate size classes. The soil C content up to 30 cm depth in the P. rigida and L. kaempferi plantations were 47.69 Mg ha⁻¹ and 61.49 Mg ha⁻¹, respectively, and were also higher in the surface soil than in the deep soil. In both plantations, macroaggregate contained more Ccontent than microaggregate did. The microbial biomass C and soil C concentrations were significantly higher (P < 0.05) in the L. kaempferi plantation than in the P. rigida plantation due to the effect of species difference. The MWD and C content tended to be greater in the L. kaempferi plantation than in the P. rigida plantation, but the differences were not significant. In this study, the soil aggregate size, microbial biomass C and soil C concentrations were positively correlated with one another.