Dynamic simulation of farmland SOC in parallel ridge valley area in eastern Sichuan in the next 30 years

The relationship between greenhouse gas emission reduction and soil carbon sequestration has become the focus of global climate change research amidst the worsening global climate change. As a core interface of terrestrial ecosystem, farmland soils have a huge potential to sequester carbon. Exploring the response and feedback of the dynamic balance of farmland soil organic carbon (SOC) to global climate change is significant in understanding the relationship between global carbon cycle and agricultural ecosystems. Dianjiang County is a typical representation of parallel ridge valley area in eastern Sichuan. It is an important grain and oil producing area in Chongqing. In the process of transformation from traditional to modern agriculture, the area has been faced with double pressures of food security and increasing farmland SOC. Therefore in this region, it is very important to study farmland SOC and its dynamic change using specific climate model in the next 30 years. It provides data support and scientific basis for sustainable utilization and management of future cultivated lands in the study area. Supported by GIS regional database established for soil properties and agricultural management system, this study simulated the dynamic change in SOC in the study area for the period 2011-2041 using the biogeochemical model DNDC. The study also used the B₁ climate model within BCCR_BCM 2.0 in the IPCC AR4 report. The results showed that:1) The DNDC model fairly simulated farmland SOC and dynamic change under specific climate conditions. The correlation coefficient between the simulated and measured values was 0.981, which was significant at the 0.01 confidence level. The RMSE value of the simulated and measured values was 16%, indicating better simulated results. 2) The SOC density and storage in the 0-20 cm soil layer in the study area significantly increased for the next 30 years. The increase in carbon per unit area was 2 637.07-8 091.55 kg(C)·hm^-2 or 10%-34%, that in carbon sequestration was 2.7×10⁵-8.3×10⁵ t, and that in average increase rate was 87.9-269.7 kg(C)·hm^-2·a^-1. 3) For the next 30 years, the farmland soil in parallel ridge valley area in eastern Sichuan was generally under continuous carbon sink. In the study area, the differences among carbon sink, carbon loss and carbon relative balance gradually increased for the next 30 years.