Exploring soil ecology gradient concepts: sensitivity of ecosystem properties to symbiotic fungi in semiarid prairie

Abstract In resource-limited environments, plants are predicted to increase root mining or collaboration with nutritional mutualists. Little is known about arbuscular mycorrhizal fungi (AMF) effects on grasslands with low soil phosphorus (P) solubility. We evaluated AMF effects on plants, plant–plant interactions, plant nutrient limitation, and nutrient acquisition strategy in a series of experiments. A 5-year field experiment tested how AMF suppression affected the plant community; lichen and moss abundance; nutrient limitation and P acquisition; and soil structure and function. Fungi suppression eliminated lichens, increased mosses 410%, increased plant biomass 13% and shifted grass dominance. AMF suppression increased shoot N: P (indicator of P limitation) of Koeleria macrantha and had no effect on Hesperostipa comata N: P. Pot bioassays tested how grass coexistence was affected by three pairs of soil treatments (1) field soil inoculant (FSI) versus FSI with AMF suppression, (2) FSI versus sterilized FSI, and (3) AMF inoculant versus sterilized AMF inoculant. Koeleria outperformed Hesperostipa across treatments. Hesperostipa was likely P-limited, with 2.5 times greater N: P. Koeleria had 2.2 to 4.1 times greater shoot [Mn] (indicator of root exudation to mobilize calcium-bound P) than Hesperostipa . FSI sterilization increased shoot [Mn] of both grasses, suggesting plasticity for root mining. AMF had small effects on some grasses, but plant community composition, soil structure, and soil function were resistant (or resilient) to AMF suppression. Results provide insight to plant P acquisition strategies where soils with low organic matter and P solubility promote autonomous P-acquisition while moderate soil fertility and P lability favor AMF collaboration.