Uncertainty of organic carbon dynamics in Tai-Lake paddy soils of China depends on the scale of soil maps

Abstract

Agro-ecosystem models have been widely used to quantify soil organic carbon (SOC) dynamics based on digital soil maps. However, most of the studies use soil data of single or limited choices of map scales, thus the influence of map scales on SOC dynamics has rarely been quantified. In this study, six digital paddy soils databases of the Tai-Lake region in China at scales of 1:50,000 (P005), 1:200,000 (P02), 1:500,000 (P05), 1:1,000,000 (P1), 1:4,000,000 (P4), and 1:14,000,000 (P14) were used to drive the DNDC (DeNitrification & DeComposition) model to quantify SOC dynamics for the period of 2001⿿2019. Model simulations show that the total SOC changes from 2001 to 2019 in the top layer (0⿿30cm) of paddy soils using P005, P02, P05, P1, P4, and P14 soil maps would be 3.44, 3.71, 1.41, 2.01, 3.57 and 0.10 Tg C, respectively. The simulated SOC dynamics are significantly influenced by map scales. Taking the total SOC changes based on the most detailed soil map, P005, as a reference, the relative deviation of P02, P05, P1, P4, and P14 were 7.9%, 58.9%, 41.6%, 3.9%, and 97.0%, respectively. Such differences are primarily attributed to missing soil types and spatial variations in soil types in coarse-scale maps. Although the relative deviation of P4 soil map for the entire Tai-Lake region is the lowest, substantial differences (i.e., 22⿿1010%) exist at soil subgroups level. Overall, soil map scale of P02 provides best accuracy for quantifying SOC dynamics of paddy soils in the study region. Considering the soil data availability of entire China, P1 soil map is also recommended. This study suggested how to select an appropriate scale of input soil data for modeling the carbon cycle of agro-ecosystems.