Abstract: Invasive plants have distinct geographic regions outside of their endemic range where they can proliferate and displace native species. As invasive plants expand their ranges, some escape pathogens from their endemic range or acquire mutualisms that enhance nutrient uptake. Many invasive plants alter the soil microbial community and chemical characteristics, leaving a lasting soil legacy that influences the future of invasion. Understanding how invasive plants interact with soil communities under different soil environments can provide insight into why these species spread aggressively only in some parts of their range. We evaluated the effects of Linaria vulgaris invasion legacy in Colorado and Illinois soil to determine: Do soil characteristics explain why L. vulgaris is an aggressive invader in CO and non-aggressive in IL? We grew L. vulgaris and two IL native plants in soil collected from the Rocky Mountain Biological Lab in Gothic, CO (low N) and near Chicago, IL (high N) and compared the effects of site, invasion legacy, and N availability on plant biomass and presence in pots. We used Next Generation Sequencing to characterize AMF communities in previously invaded and uninvaded soil from the two sites.
We found evidence that L. vulgaris has a positive soil-feedback in CO soil and a negative soil-feedback in IL soil, which follows patterns of invasion aggressiveness. Linaria vulgaris only grew in 85% of pots in CO soil containing invaded soil and in 40% of pots containing uninvaded soil (P = 0.03). However, in IL soil, L. vulgaris only grew in pots containing uninvaded soil. Nitrogen fertilization did not affect L. vulgaris success in any treatment, indicating that nitrogen availability is not responsible for the positive soil-feedback. Native plant root biomass in CO soil was 49% greater in uninvaded than invaded soil, indicating that L. vulgaris invasion negatively impacts native plant success (P = 0.05, df = 21, t = -2.1). AMF communities were significantly different between CO and IL (F = 10.6, R2= 0.12, P = 0.001), but not different between invaded and uninvaded soil (F = 0.62, R2= 0.01, P = 0.86), illustrating that L. vulgaris invasion most likely does not change AMF communities, but invasion could still be influenced by already existing AMF community composition. This study provides evidence for the influence of soil legacy effects in delimiting the range of Linaria vulgaris invasion. However, we did not find strong evidence that L. vulgaris invasion influences AMF communities.
