Alfalfa-associated AM fungal intraradical and extraradical communities response differently to P addition

To investigate the responses of root-/ soil- associated AM fungal communities to P addition, we examined the impact of long-term P fertilization on the intraradical and extraradical mycorrhizal communities in an alfalfa field which was treated with four P fertilization levels (P0 0 P2O5 ha-1; P1 75 P2O5 ha-1; P2 105 P2O5 ha-1; P3 225 kg P2O5 ha-1) for over 10 years. We found that AM fungal colonization declined significantly at the highest P level (P3) and negatively related to soil AP, suggesting a decreased reliance on AM fungi at this high P level. AM fungal diversity in roots also declined in P3. The indicator species (belonged to Diversisporaceae) in roots increased in relative abundance in the P1 treatment. Although P addition had no significant effect on OTU richness and AM fungal community composition, we found that pH and SOM structured roots and soil mycorrhizal communities respectively. In conclusion, P input affected root and soil AM fungal communities differently. Further research is needed to determine how individual AM fungal species may respond to P fertilization, and how this may impact plant productivity.