Mycorrhizal colonization and growth of Phragmites australis in an intermittent wetland

Arbuscular mycorrhizal (AM) and dark septate endophytic (DSE) fungal colonization of Phragmites australis roots and its relation to plant productivity parameters was investigated in an intermittent karst wetland Lake Cerknica (Slovenia) with seasonal water level fluctuations. Mycorrhizal colonization was determined five times in 2008–from the beginning to the end of the growing season–in three reed stands with large differences in soil parameters and water level changes. AM and DSE colonization varied significantly between sampling plots and during the growing season (7% < frequency < 87%). The flooding of two of the three reed stands decreased mycorrhiza early in the growing season, but further flooding had no additional effect. Levels of DSE colonization were high in the beginning and the end of the growing season, while a peak in AM colonization was observed towards the end. The observed positive in situ correlation between mycorrhizal colonization and P. australis growth parameters does not allow final mechanistic conclusion: both P. australis and mycorrhiza could be beneficial.