Effects of an invasive plant on mycorrhizal fungi in the tallgrass prairie and detection by hyperspectral imagery

Tallgrass prairies are degraded ecosystems vulnerable to invasion. Lespedeza cuneata (sericea) is an invasive plant overtaking prairies through biological mechanisms, such as abundant seed production, associations with nitrogen-fixers, and allelopathy. Using above-to-below-ground linkages, sericea can alter the composition of below-ground microorganisms, such as arbuscular mycorrhizal fungi (AMF). AMF boost plant success by improving nutrient uptake, defense, and growth in exchange for carbon. A homogeneous AMF composition from sericea monocultures could continue degrading prairies. However, prescribed fires are a common management method used in prairies to control sericea invasion. As prairies are heterogeneous with variations in plant composition and edaphic conditions, large-scale studies are needed to understand ecosystem-level invasion effects. We combined hyperspectral imagery with vegetation and soil fungal datasets for this large-scale study. We studied sericea invasion at the Joseph H. Williams Tallgrass Prairie Preserve. Plant surveys assessed invasion levels across 100 plots from which soil samples were collected to determine belowground characteristics. Soil samples were sieved to extract spores. Fungal DNA was extracted from each soil sample using a Qiagen PowerPro Soil Kit and was sent for DNA sequencing using Illumina sequencing and fungal-specific primers. From this, operational taxonomic units (OTUs) were filtered and clustered. Total spore counts and DNA read numbers were analyzed using regression analyses. A multivariate test analyzed spore and OTU composition. A Mantel test determined if hyperspectral imagery detected changes in spore composition, and a linear regression tested if hyperspectral diversity correlated with spore abundance. Sericea invasion significantly altered the communities of AMF, and marginally lowered the diversity of symbionts. Burn did not affect sericea invasion but did alter fungal communities as well. Nitrogen was increased by sericea invasion, and this greater nitrogen content also changed the fungal community. Hyperspectral diversity was significantly correlated with spore abundance. These results indicate that sericea significantly alters fungal communities of tallgrass prairies across large spatial scales, and hyperspectral imagery detects certain changes. AMF improve plant success, and when interactions are disrupted, native diversity is worsened. Our results demonstrate the potential for hyperspectral imagery to detect invasion and below-ground impacts.