Phosphorus addition reverses the negative effect of nitrogen addition on soil arthropods during litter decomposition in a subtropical forest

The increase in the nitrogen/phosphorus (N/P) ratio with rising N deposition is changing the biodiversity and function of terrestrial ecosystems at an unprecedented speed. However, the specific effects of P addition and its interaction with N on soil arthropods during litter decomposition in forests are unclear. A two-year experiment was carried out in western China to examine the effects of N and P addition on soil arthropods during litter decomposition. We applied a factorial design in a litterbag experiment combining two levels of low and high N and P alone addition (LN, HN, LP, and HP) and their coaddition (LNLP, LNHP, HNLP, and HNHP), including a no-addition control treatment (CK). The results show that soil pH, litter microbial biomass carbon (MBC), soil arthropod group number (G), individual number (I), diversity index (S), and richness index (M) were lower in the LN and HN treatments than in CK. Compared with CK, the LP and HP treatments reduced I but did not alter G, S, and M. The MBC, soil pH, and G, I, S, and M were higher and the cellulose and lignin concentrations and soil arthropod dominance index values were lower in the LNLP, LNHP, HNLP, and HNHP treatments than in CK. The positive effects of the LNLP, LNHP, HNLP, and HNHP treatments on the soil arthropods were related to the increased MBC and soil pH and decreased cellulose and lignin concentrations and litter N/P ratio. The litter N/P ratio was inversely related to the soil arthropod diversity. In conclusion, the negative effect of N addition on soil arthropod diversity during litter decomposition was reversed when P was added by shifting the MBC, cellulose and lignin concentrations, soil pH, and litter N/P ratio. Thus, increased P availability under rising N deposition scenarios may enhance soil arthropod diversity in this forest. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The N/P ratio in terrestrial ecosystems is changing due to increasing N deposition, affecting the biodiversity and function of ecosystems. The effects of P addition and its interaction with N on soil arthropods during litter decomposition in forests are unclear. A two-year experiment in western China showed that adding both N and P had positive effects on soil arthropods, increasing microbial biomass carbon and soil pH while decreasing cellulose and lignin concentrations.