Ectomycorrhizal Diversity Increases P Uptake Efficiency of European Beech

Increases in summer droughts and N deposition have raised concerns of widespread biodiversity loss and nutrient imbalances, but our understanding of the ecological role of ectomycorrhizal fungal (ECMF) diversity in mitigating root functions remains a major knowledge gap.

We used different global change scenarios to experimentally alter the composition of indigenous ECMF communities colonizing European beech saplings and examined the consequences for P uptake (H₃³³PO₄ feeding experiment) and use efficiencies of trees. Specifically, we simulated increases in temperature and N deposition and decreases in soil moisture and P availability in a factorial experiment.

We found that ECMF α diversity is a major factor contributing to root functioning under global change. P uptake efficiency of beech significantly increased with increasing ECMF species richness and diversity, as well as with decreasing P availability. As a consequence of decreases in ECMF diversity, P uptake efficiency decreased when soil moisture was limiting. By contrast, P use efficiencies were a direct (positive) function of P availability and not of ECMF diversity.

We conclude that increasing summer droughts may reduce ECMF diversity and the complementarity of P uptake by ECMF species, which will add to negative growth effects expected from nutrient imbalances under global change.