Objective This paper aims to investigate the accumulation and transformation characteristics of soil organic carbon (SOC) components in Eucalyptus spp. plantations of different continuous planting generations, so as to reveal the impact of environmental factors on accumulation and transformation processes of SOC components, thereby providing a scientific basis for improving Eucalyptus spp. productivity and soil management.

Method Taking the first, second, and third generations of Eucalyptus spp. plantations in Bobai Forest Farm, Bobai County, Guangxi Province of southern China as the research objects, soil samples from 0–40 cm depth were collected. The soil was fractionated into aggregates of > 2 mm, 1–2 mm, 0.25–1 mm, and < 0.25 mm using dry sieving to evaluate soil aggregate stability. The contents and storage of organic carbon components, including active organic carbon, slow organic carbon, and inert organic carbon in different aggregates were measured. Redundancy analysis (RDA) and partial least square structural equation modeling (PLS-SEM) were used to identify the key factors affecting the accumulation and transformation of SOC.

Result (1) Continuous planting significantly reduced the stability of soil aggregates and decreased the content and storage of various organic carbon components. (2) The contents of each SOC component decreased with increasing aggregate particle size, while the storage distribution showed the opposite trend. (3) RDA and PLS-SEM demonstrated that soil aggregate stability was the main factor influencing SOC accumulation. Continuous planting inhibited the transformation of inert organic carbon into active organic carbon, leading to a decline in the overall effectiveness of SOC.

Conclusion Continuous planting primarily regulates the accumulation and transformation of SOC components in Eucalyptus spp. plantations by altering the distribution and stability of soil aggregates. These findings enhance the understanding of regulatory mechanisms of soil aggregates in accumulation and transformation processes of SOC in Eucalyptus spp. plantations.