MOVED TO WED, COS 78-4, 2:30 PM // Arbuscular mycorrhizal fungal P provision to plants not dependent on fungal sensitivity to soil P
Phosphorus (P) is an important potentially limiting nutrient for plant growth, and associations with arbuscular mycorrhizal fungi (AMF) often enhance its uptake by plants. The fraction of soil P thought to be available for uptake by plants and AMF is that which is frequently extracted by NaHCO3. We tested this assumption and also explored relationships between AMF community composition, soil P pools, and plant P storage. We visited 58 temperate agricultural grasslands in Germany and collected data on AMF diversity, P storage in aboveground biomass, and soil P availability in five fractions (NaHCO3-Pi, NaHCO3-Po, NaOH-Pi, NaOH-Po, and HCl-P) using the Hedley sequential extraction procedure. This is the first analysis of how AMF communities are structured by P availability to use such a comprehensive P profile. We performed redundancy analysis (RDA) corrected for spatial autocorrelation with principal coordinates of neighborhood matrices to test for effects of P availability on AMF community composition. We then ran path models to further clarify how AMF community composition was related to soil P pools and plant P storage.
The contrast between labile (NaHCO3-Pi, NaHCO3-Po, and NaOH-Pi) and recalcitrant (NaOH-Po and HCl-P) P fractions was important for structuring AMF communities, but not the contrast between inorganic and organic forms of P. Our data suggest that AMF interactions with soil P pools and AMF contribution to plant P storage are regulated by independent processes. This therefore suggests taxonomic decoupling of two important AMF functions: P uptake from soil and P delivery to plants.