COS 203-5 - Arbuscular mycorrhizal communities in tallgrass prairie restorations vary with restoration age and bison grazing

Abstract: Mycorrhizal fungi form symbioses with the majority of land plants but are often overlooked in restorations despite being critical for restoration success. Agricultural practices such as tillage and chemical inputs decrease the level of mycorrhizal colonization impacting later restorations. To assess if arbuscular mycorrhizal (AMF) restoration occurs in conjunction with tallgrass prairie restoration, we sequenced the AMF community at the Nachusa Grasslands over a period of six years. This site consists of 17 prairie restorations of varying age and two remnant sites with bison grazing on half of the sites. We also sampled two adjacent agricultural fields which have been continuously row cropped. We hypothesized that agricultural fields would have a significantly less diverse AMF community than adjacent restorations and remnants. Additionally, we anticipated that older restorations would have communities that resembled remnant sites.

We found significantly different (p = 0.05) evenness by sample type (agricultural, restoration or remnant). This was caused primarily by a high number of very abundant OTUs with in each site type. In agricultural fields 18 OTUs made up 75% of the relative abundance of the community. In restored and remnant sites 33 OTUs made up 75% of the community. Due to this, we decided to analyze the abundant (at least 1% of relative abundance, or 30 OTUs overall) and rare communities separately. Within the abundant community, there was a consistent effect of year (p = 0.001) on agricultural and restored sites but not remnant sites suggesting that remnant sites have a more stable AMF community. Furthermore, there is an effect of age category (old, middle and young, p = 0.038) and a year by bison interaction (p = 0.003) Within year, there is an inconsistent effect of bison grazing on restored sites (p > 0.05) and age category (p > 0.05) on AMF community composition. Within rare communities, there was an effect of year (p = 0.001), restoration age (p = 0.043) as well as an age by bison effect (p = 0.003). These results suggest that the AMF communities in tallgrass prairies are being actively restored. As the restoration ages, the more likely it is to resemble the remnant sites in both diversity and composition. However, this effect dampens with bison access as grazing seems to homogenize the differences in diversity caused by restoration age in sites without bison access. Bison grazing may increase the speed at which AMF communities can be effectively restored.