Soil spatial heterogeneity created by river–sea interaction influences Tamarix chinensis root features in the Yellow River Delta

Salt-tolerant Tamarix chinensis roots are crucial in preserving wetland soil and carbon sequestration, which is essential for wetland ecology. Soil-water-salt conditions influence the growth of these roots in coastal saline areas, but the specific factors and their effects remain unclear. Using principal component and partial least square–structural equation modelling (SEM) methods, we studied T. chinensis root features in six Yellow River delta communities. Results showed varied root features across locations, with larger roots further inland. Root growth negatively correlated with soil texture and salinity and positively with groundwater levels. Soil texture and salinity decreased with distance from the coast, while groundwater increased with distance from the Yellow River. This suggests that geographical location influences soil-water-salt conditions, impacting root characteristics. The principal component analysis–derived root feature index captured 56.7% of root feature variation. SEM revealed geographical locations indirectly influence root features, with the Yellow River's proximity primarily affecting them through groundwater and coastal distance influencing via soil sand content and salinity. The study underscores the importance of these findings for wetland conservation and ecology.