Ecological factors and arbuscular mycorrhiza of Ambrosia artemisiifolia , an invasive plant species colonizing anthropogenic habitats –example from Upper Silesia, Poland

Ambrosia artemisiifolia (Common ragweed), an invasive alien plant which spreads on a large scale on farmland, and along roads and railway tracks in many European countries, causes economic losses in agriculture and brings increased sensitization to ragweed allergens in human populations (Tokarska-Guzik et al., 2011). The aim of the presented study was to monitor the actual state of the spread of A. artemisiifolia in Upper Silesia, using the example of selected ragweed populations occupying different anthropogenic habitats, namely: a roadside (O – Orzesze and Ż – Żory) and a railway track (TG – Tarnowskie Gory). The analysis of ragweed biometrical indicators, ecological factors and arbuscular mycorrhiza allow the prediction of its future trends of spread on a regional scale, and has implications for control strategies. The results of the plant's biometric characteristics showed that the average values of morphometric attributes (length of stem, number of lateral branches, length of male and female inflorescences, length of the main root, dry weight) were higher for the roadside population (Ż) compared to the railway population (TG) and the second roadside population (O). Soil analysis implied lower levels of organic carbon, phosphorus and nitrate nitrogen in the roadside population (Ż), in comparison to the other populations. These results contradict the higher growth of ragweed in the Żory site, and indicate that future studies are still required for its explanation. Ambrosia artemisiifolia populations in Upper Silesia were found to have arbuscular mycorrhizal colonization, confirming previous reports from Europe. Mycorrhizal plants of this species were found in all the investigated populations. Arbuscular mycorrhizal structures like arbuscules, as well as vesicles, coils and hyphae, were found in the roots of A. artemisiifolia. The intensity of mycorrhizal colonization was very high in all stands but slightly higher in the railway population. The obtained results suggest that ecological factors like soil properties and mycorrhiza can have a positive impact on ragweed plants' vigor. However, its invasive success can also be influenced by other factors such as the age of the population and type of habitat.