Growth and mycorrhizal colonization of two grasses in soils with different inundation histories

Plant growth, N nutrition and mycorrhizal colonization of a native and invasive grass on two soils with differing histories of inundation were studied. The soils, collected from Lake Mokoan in south eastern Australia were last flooded 1 and 18 years prior to sampling, and differed in mineral N pools and plant-available P. The exotic pasture grass Phalaris aquatica and the native grass Austrodanthonia caespitosa grew readily in both soils in a glasshouse experiment, although both generally had lower biomass on the most recently exposed soil. The differences in growth of both species on the two soils can be explained by N limitation. Mycorrhizal colonization, while different between species, was similar between sites, indicating that viable propagules of arbuscular mycorrhizal fungi were present at the new-shore site. Taken together, this study indicates that both the native and exotic grass species have the potential to grow on the recently exposed soils at Lake Mokoan. This site will likely require active management to avoid invasion by the exotic grass P. aquatica, and if native plant communities are to be restored. The data presented here will be important in developing future restoration strategies.