PS 27-121
Use of biochar soil amendments and inoculation with arbuscular mycorrhizal fungi in prairie restorations
Arbuscular mycorrhizal (AM) fungi in the soil form mutualisms with plants that play an important role in maintaining diverse plant communities in prairie ecosystems. Planting ‘nurse’ plants inoculated with species of prairie AM fungi into prairie restorations is a promising way to aid establishment of late successional plant species that typically rely on mycorrhizal associations. However, little is known about how inoculated AM fungi spread through the soil of prairie restorations. Separately, the addition of biochar, or partially burned plant material, to the soil can alter AM fungal abundance and sequester carbon. Prairie plant and AM fungal species may be well adapted to biochar because it naturally occurs in prairies due to periodic fires. We established restoration field plots to measure the effects of inoculation with AM fungi and different biochar application rates on: 1) prairie plant growth and community composition, 2) soil structure and nutrient availability, and 3) the spread of inoculated AM fungi through the soil. Biochar was tilled into the soil before planting at a rate of either 10 tons/ha (low biochar) or 20 tons/ha (high biochar). Seedlings of nine prairie plant species representing multiple functional groups were each inoculated with either a community of eight prairie AM fungal species or with a sterile sand control and were then planted in a grid at the center of each plot to act as nurse plants; in the outer portion of each plot we distributed a diverse seed mix but no seedlings. We then compared plant community composition, soil structure, and soluble reactive phosphorus (SRP) flux between the center of each plot where the inoculated nurse plants were located and the outer portion of the plot.
Results/Conclusions
During the first growing season, six nurse plant species grew significantly taller when inoculated with prairie AM fungal species regardless of biochar treatment. However plant species diversity did not change significantly between treatments or with location in the plot. Soil aggregate stability increased near nurse plants and with low biochar, but neither change was statistically significant. Soil from the high biochar treatment had a significantly lower fine (<250 µm) size fraction, indicating an increase in the proportion of larger size fractions; there were also significantly lower medium (0.5–2 mm) size fractions near nurse plants. Fluxes of SRP through the soil did not change with treatment or location in the plots. We will follow these responses over the next several years.