Opposing responses of soil element interactions to high macro-nutrient levels and combined macro- and micro-nutrient enrichment

The intricate interconnections among various ecosystem components are essential for maintaining ecosystem stability and sustainability. These interactions are often represented as networks reflecting biogeochemical cycling. Soil element networks are sensitive to global environmental changes; however, their responses to varying nutrient levels remain unexplored. Here, we compiled measurements of soil concentrations of 13elements, which are carbon (C), nitrogen (N), phosphorus (P), potassium (K), calcium (Ca), magnesium (Mg), sulfur (S), sodium (Na), zinc (Zn), manganese (Mn), iron (Fe), copper (Cu) and boron (B)—from 40 Nutrient Network sites worldwide. Using a natural gradient approach, we assessed the complexity of soil element networks in relation to varying nutrient supply levels, including single-element, micro-nutrients (Ca, Mg, S, Na, Zn, Mn, Fe, Cu, B), macro-nutrients (C, N, P, K), and all-nutrient combinations.Our results demonstrated that soil element network complexity did not differ under different levels of single macro-nutrient or combined micro-nutrient combinations. However, it decreased noticeably with higher levels of macro-nutrient combinations but increased with higher levels of all-nutrient combinations. These findings provide novel insights into soil ecosystem functioning and highlight the critical role of nutrient interactions in maintaining ecological balance.