Phosphorus addition regulates the responses of soil multifunctionality to nitrogen over-fertilization in a temperate grassland

Aim: Nitrogen (N) and phosphorus (P) are two major limiting factors in terrestrial ecosystems. Excessive N applications alter ecosystem functions by causing nutrient imbalances with P. Yet, little is known about why and how the balance between N and P regulates soil multifunctionality –the simultaneous provision of multiple soil functions–. Methods: We explored how P additions regulated the responses of soil multifunctionality to different levels of N fertilization (10, 20, 40 g N m⁻² yr⁻¹) using a mesocosm experiment in a temperate grassland in China. Results: Nitrogen alone and P addition increased multifunctionality at rate of ≤10 and 20 g N m⁻² yr⁻¹, respectively. However, the magnitude of positive effects decreased with N additions over this level. P additions increased multifunctionality resistance to N at low rate of ≤10 g m⁻² yr⁻¹ compared to higher N levels. Soil N:P stoichiometry and plant diversity played dominant roles in regulating soil multifunctionality. Conclusions: We found that a balanced combination of N and P additions (20:10) can help maintain the highest multifunctionality in this temperate grassland. The results provide new insights that through P addition, we could better manage soil multifunctionality and increase its resistance to expected fertilization scenarios (≤ 10 g m⁻² yr⁻¹).