Nutrient and arbuscular mycorrhizal amendments in prairie restoration

Prairie restoration emerged recently as a vegetation management technique and restoration protocols are quickly evolving to incorporate new, more ecologically sound and efficient plant propagation methods. The ability of fertilizers and arbuscular mycorrhizal fungi (AMF) to enhance native plant growth was tested at a wet prairie site in central Minnesota that had previously had a restoration failure.;The Beltsville hydroponic AMF inoculum production method was modified and studied as a means to produce prairie AMF inoculum. Inoculum produced by this method had fewer colonizing fungal spores than desired. This system has potential for AMF inoculum production, should culturing conditions be improved.;A one-time fertilizer and AM inocula application was tested at a restoration site in central Minnesota. Three fertilizer regimes (inorganic fertilizer, slow-release fertilizer [SRF], and an unfertilized control) were combined with four AMF inocula regimes (commercial inoculum/furrows, local inoculum/broadcast, local inoculum/furrows and uninoculated/furrows). Three measures were used to assess potential amendment benefits: biomass, species composition changes and diversity.;Changes in plant biomass were significant for the slow-release fertilizer (SRF) treatment, while the inorganic fertilizer treatment had little affect on biomass. SRF treatment corresponded to increased undesired forb and grass biomass for two years following application. AMF inoculation did not significantly affect biomass.;Species abundance and diversity were significantly altered by SRF. Inorganic fertilizer did not change plant community composition. Plants that increased in abundance were mostly weedy annual grasses, whereas those decreasing in abundance were typically perennial native grasses. AM inoculation treatments did not affect species abundance, however functional group abundance was slightly altered in a few instances. The changes in abundances may or may not have been due to the AMF propagules applied in the AM treatment regimes.;Overall, the restoration site studied did not significantly benefit from fertilizer or AM fungal amendment. Nutrients added in the inorganic treatment were likely leached; while the SRF treatment reduced native plant abundance and biomass. Other similar studies indicate that fertilization is likely not helpful, but some AMF inoculation studies suggest some benefits. Restoration site conditions appear to be an important factor determining whether fertilization or fungal amendments are helpful.