Arbuscular mycorrhiza of introduced and native grasses colonizing zinc wastes: implications for restoration practices

The analysis of mycorrhizal status of grasses introduced under conventional phytoremediation programmes (including covering of the waste area with a layer of uncontaminated soil and watering) and of grasses that spontaneously established in later successional stages, was carried out on the slopes of the 1- to 30-year-old tailings of ZG Trzebionka Mining Company located near Chrzanzow (southern Poland). Most grasses were mycorrhizal and the parameters of mycorrhization were higher on the older parts of the waste. Grasses selected for restoration practices were well developed only if the waste was covered with a layer of soil and continuous irrigation took place, both being expensive practices. The field experiment showed that the introduction of standard inoculum containing mycorrhizal fungi indeed improved the development of grasses during early stages, but still was not effective enough due to high erosion of the substratum. A slight improvement was observed when AgroHydroGel was used to lock moisture in the soil, but the plants did not survive for longer time periods. On the contrary, much better results were obtained when vegetatively multiplied grasses selected from specimens originating from natural succession were used to stabilize the vegetation on the bare industrial waste.