Interactions between arbuscular mycorrhiza and the growth of the invasive alien annual Impatiens parviflora DC: A study of forest type and soil properties in nature reserves (S Poland)

Invasive alien plants can benefit from interactions with mycorrhizal fungi in their spread and competition with native species. Hitherto, little was known about the ecological conditions related to the presence of arbuscular mycorrhiza (AM) in the annual invasive alien species Impatiens parviflora. The soil properties, plant morphometric features, mycorrhizal status, degree of root colonization and morphotype of arbuscular mycorrhiza were evaluated in different forest communities: alder-ash carrs, oak-hornbeam forests, beech forests and mixed forests. Mycorrhizal plants of this species were found in all of the analyzed forest communities and the Arum-type of morphology was reported. The largest and most fecund individuals as well as the highest mycorrhizal frequency (F%) and relative arbuscular richness (A%) were recorded in individuals from populations growing in alder-ash carrs and oak-hornbeam forests. A comparison of sites where non-mycorrhizal AM− and mycorrhizal AM+ individuals of I. parviflora were found revealed that AM+ plants grow on soils with a higher magnesium content and that were more alkalized. The Pearson and Spearman correlations yielded positive significant coefficients with respect to the relationships between mycorrhizal frequency and pH. The arbuscule richness in root fragments where mycorrhiza was present (a%) was found to be positively correlated with pH and Ellenberg moisture as well. However, the ratio of C/N was negatively correlated with F% and a%. The mean height of plants was positively correlated with (F%), relative mycorrhizal root length (M%) and relative arbuscular richness (A%). The latter were also positively correlated with the number of flowers and fruits. The study revealed that I. parviflora is not an obligatory mycorrhizal plant and AM seems to influence the growth and reproduction of this plant, and that it can indirectly enable the spread and naturalization of the species.

► The study revealed that invasive alien annual plant species Impatiens parviflora is of Arum-type of arbuscular mycorrhiza AM. ► Mycorrhizal plants grow on soil with a higher magnesium content and higher pH in forest communities. ► Mycorrhizal colonization was positively correlated with number of fruits and flowers in this species. ► I. parviflora is not an obligatory mycorrhizal plant, however AM seems to influence vigorousness of the species.