Enhanced decoupling of multiple elements in coastal reclaimed soils following intensive agricultural use in eastern China

Abstract

Understanding the biogeochemical coupling of multiple soil elements is essential to evaluating soil health and ecosystem stability. However, the effects of long-term coastal wetland reclamation on soil elemental enrichment and geochemical interactions remain poorly understood. This study aimed to elucidate the evolution of multi-element behavior in soils across a chronosequence (0, 10, 30, 65, and 90 years) of coastal reclamation. We conducted a comprehensive analysis of 31 elements (including As, Al, B, Br, Ca, Cd, Cl, Co, Cr, Cu, F, Fe, Hg, I, K, Mg, Mn, Mo, N, Na, Ni,C, P, Pb, Rb, S, Sb, Si, Sn, Sr, Zn) in the soils, focusing on exploring the evolution of element enrichment, dispersion, correlation, and multi-element coupling (MEC) along the reclamation gradient during an increase in reclamation duration. The results revealed that several elements were significantly enriched after reclamation, whereas others remained below background levels. Fertilization, irrigation, and intensive cultivation significantly alter the soil geochemical processes and elemental interactions. With the extension of the reclamation duration, the concentrations of organic carbon (SOC), N, P, Zn, Cu, Cd, Hg, F, and Cl increased, whereas those of S, Na, Mg, Ca, Cr, Mn, Sr, Br, As, and Mo decreased, highlighting the regulatory role of agricultural activities in shaping elemental distribution. Temporal declines in the number of positive correlations, mean correlation coefficients, and MEC values suggest progressive weakening of element coupling under human influence. Major elements maintained higher correlation strengths and coupling degrees than minor elements, indicating greater resistance to anthropogenic disturbances. Partial least squares path modeling (PLS-PM) revealed that while MEC is primarily regulated by stable natural factors such as soil texture, human activities also serve as key drivers of elemental decoupling because of their continuous and cumulative impacts on soil element interactions. This study provides novel insights into the long-term alteration of geochemical interactions in reclaimed soils and emphasizes the need for sustainable management strategies to preserve soil multifunctionality in coastal reclamation regions.