Native plant abundance, diversity, and richness increases in prairie restoration with field inoculation density of native mycorrhizal amendments

Abstract

Ecological restoration efforts can increase the diversity and function of degraded areas. However, current restoration practices cannot typically reestablish the full diversity and species composition of remnant plant communities. Restoration quality can be improved by reintroducing key organisms from the native plant microbiome. In particular, root symbionts called arbuscular mycorrhizal (AM) fungi are critical in shaping grassland communities, but are sensitive to anthropogenic disturbance, which may pose a problem for grassland restoration. Studies of mycorrhizal amendments include inoculation densities of 2–10,000 kg of inocula per hectare. These studies report variable results that may depend on inocula volume, composition, or nativeness. Here we test eight different densities of native AM fungal amendment, ranging from 0 to 8,192 kg/ha in a newly installed prairie restoration. We found that native plant establishment benefited from native mycorrhizal inocula, resulting in improvements in native plant abundance, richness, and community diversity. Moreover, the application of very low densities of native mycorrhizal inocula, as suggested on commercial mycorrhizal products, were ineffective, and higher concentrations were required to benefit native plant abundance and community diversity. These data suggest that higher densities of mycorrhizal amendment or perhaps alternative distribution methods may be required to maximize benefits of native mycorrhizal amendments in restoration practices.

Manipulating plant microbiomes in the field: Native mycorrhizae advance plant succession and improve native plant restoration

“…Recent meta‐analysis suggests that the benefits of inoculation may improve overtime (Neuenkamp et al., 2019). To be used as an effective restoration tool, more work is needed to assess whether applying native mycorrhizal inoculum can be effective using other application techniques likely to be utilized for large‐scale restoration, such as via seed drill, the use of trap cultures and other broadcast methods (Koziol et al., 2020; Vahter et al., 2020; Wubs et al., 2016).…”

Arbuscular Mycorrhizal Fungi Taxa Show Variable Patterns of Micro-Scale Dispersal in Prairie Restorations

“…Although whether or not these inocula had a significant impact on the plant community differed between year and site, when there was a significant effect, it included an increase in diversity and richness in AMF-inoculated plots (Supplementary Figures S7, S8; Figure 6), suggesting these soil amendments have the potential to alter the plant community at scales beyond the nurse plant level. Past work has also indicated that the presence of specific fungi in the field can increase seed recruitment, diversity, and native richness (Koziol and Bever, 2017) and that these benefits of AMF increase with the density of native AMF inocula (Koziol et al, 2020).…”

Restoration, soil organisms, and soil processes: emerging approaches

“…respiration, C and P exoenzyme activities), which may help to increase plant cover. Others experimented with inoculating restoration sites with soil microbial amendments (Koziol et al 2020; Lance et al 2020) or with intact soil containing desirable microbial communities (Grman et al 2020; Remke et al 2020).…”

“…Grman et al (2020) observed that establishment of seeded native legumes was improved with inoculation from microbes from remnant prairie soil. In addition, Koziol et al (2020) found that in midwestern US grasslands, native mycorrhizal inoculum benefited the recovery of native plant species, but that a higher dose of inoculum was required to produce positive results than is typically recommended by commercial fungal inoculation. Although there are currently commercially available soil microbial inoculants, Lance et al (2020) found that the application of commercial fungal inoculants resulted in decreased fungal abundance and tree performance.…”