Spatial distribution, influencing factors and contribution to carbon emission reduction of topsoil organic carbon in Chongqing, China

This paper is the result of environmental geological survey engineering.

Objective Natural geological carbon sinks mostly consist of soil and karst carbon sinks, and the main form of carbon’s participation in the carbon cycle in soil is organic carbon. Therefore, the study of topsoil organic carbon has great significance for increasing soil carbon sink and achieving the "carbon peaking and carbon neutrality" goal.

Methods Based on the data of a multi−objective regional geochemical survey, this paper analyzed the spatial distribution of topsoil organic carbon density in Chongqing with the geostatistical method, studied the influencing factors and importance of soil organic carbon density by one−way ANOVA and classification regression tree and evaluated the carbon sequestration and emission reduction potential of the farmland soil with the model approach.

Results The average density of topsoil organic carbon in the study area was 2.75 kg/m² , and the spatial distribution had a moderate degree of spatial autocorrelation, showing a distribution pattern of being high at the north and south ends and low in the middle. Altitude, temperature and soil type were the main factors affecting the organic carbon density, followed by precipitation and land use method. The carbon sequestration potential of farmland topsoil was about 36.88 Tg C, equivalent to 24.10% of Chongqing's carbon emissions from energy consumption in 2018.

Conclusions The soil organic carbon density was relatively high in cool and humid high−altitude areas, in Chongqing; and forests, grasslands, and paddy fields can help with the accumulation of soil organic carbon among different land use methods. Before the carbon balanceis achieved, the farmland soil, has a "carbon sink" effect as a whole, absorbing carbon from the air.