Projections of soil salinization and organic carbon dynamics in the Yellow River Delta under future scenarios

Soil salinization and soil organic carbon (SOC) critically influence soil quality. However, their future dynamics under climate change remain uncertain. Based on 214 soil samples (soil salt content: 0.03 %-3.05 %; SOC: 2.23 g/kg-16.65 g/kg) and multi-source data, the Back propagation neural network was used to construct a model of soil salinity and SOC stock to a depth of 20 cm, and SOC in Yellow River Delta (YDR) in 2023. The Space-For-Time Substitution method was used to predict salinization and SOC alterations in YDR in 2050–2100 under the shared socio-economic pathways (SSP119: Low-emissions scenario with global warming limited to 1.5°C, SSP245: Medium-emissions scenario reaching 2.7°C warming by 2100). Results showed compared to 2023, under SSP119 the annual mean temperature and precipitation during 2050–2100 show an initial increase followed by decrease, while under SSP245 they exhibit a continuous increasing trend. The proportion of soil salinization in 2023 was 83.22 % (The proportion of the region with salt content exceeding 0.1 %), soil salinization was exacerbated to varying degrees in all future scenarios, with a significant increase in areas of High Salinity (salt content >0.6 %). SOC stock (13.92 Tg in 2023) displayed different future patterns, peaking then declining under SSP119 but gradually increasing under SSP245. Soil fertility in the YRD is deemed low, with area of high SOC is extremely rare (>17.4 g/kg). Areas with low SOC typically exhibit severe salinization. Consequently, these findings highlight the need for adaptive water management and carbon sequestration strategies to sustain agriculture in saline-alkali ecosystems.