Response of belowground communities to short-term phosphorus addition in a phosphorus-limited woodland

Aims: Soil biota regulate essential ecosystem processes but our understanding of how soil fertility constrains biotic interactions remains limited. We investigated belowground responses to short-term phosphorus (P) fertilization in a P-limited woodland. Methods: Ten Eucalyptus tereticornis were randomly selected and five fertilized with superphosphate equivalent to 50 kg P ha−1 over 6 months. We estimated aboveground (understory) and belowground plant biomass, and collected samples for soil chemistry, arbuscular mycorrhizal (AM) root colonization, soil fungal abundance and community composition, and extraction of nematodes and microarthropods. Results: P-fertilization increased root biomass, abundance of non-AM fungi, and abundances of Collembola, and altered fungal community structure, but was associated with a decrease in predatory nematodes. Structural equation modelling indicated that effects on Collembola and fungal abundances were mediated by direct effects of the fertilizer treatment and/or indirect effects via root biomass responses. However, fungal community compositional changes and reductions in predatory nematodes resulted primarily due to fertilization-mediated changes in soil pH. Conclusion: Our study shows that understory plant communities and soil biota are P-limited at the study site but that some biotic groups appear to be more sensitive to changes in soil pH than to increases in P availability.