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The intermittent Lake Cerknica comprises a variety of wetland habitats, which support numerous species, many of them included on the Red List. The exchange of wet and dry periods influences the through-flow of energy and the turnover of matter in the lake. In the last five decades, the water level fluctuations were highly variable. Since 1961 the May and June water levels have shown a decreasing trend line, in October the trend line revealed an increase, while from November to February no changes of trend could be observed. High water levels in winter and during the peak vegetation season negatively affected reed productivity. The decomposition of reed leaves increased with the wetness of the survey location, while the soil mineralisation rate was only slightly related to soil wetness. In comparison to the tributaries, the lake water contained relatively low amount of nutrients, which was a consequence of a densely vegetated area.Keywords Decomposition · Evapotranspiration · Intermittent lake · Phragmites australis · Wetland habitats IntroductionLake Cerknica is an intermittent wetland appearing at the bottom of the Cerknica polje karst depression. It is characterised by extreme inter-annual water level fluctuations, which are the result of a high precipitation rate and water runoff into an extensive underground drainage system in carbonate rocks. The catchment area of the lake extends over 475 km 2 . The majority of the lake's inflow consists of karstic waters (80%), while only one tributary brings surface water (15%). The amount of water in the lake depends on precipitation and potential evapotranspiration of the

Environmental conditions in wetlands were long thought to suppress mycorrhizal fungi and it has been assumed that mycorrhiza in wetlands is limited and is of little significance. This contribution summarises the presence of arbuscular mycorrhizal (AM) fungi and dark-septate endophytes (DSE) in different habitats of the intermittent Lake Cerknica. Mycorrhizal colonisation of wetland plants from the following wetland habitats was analysed: (1) frequently inundated small depressions in the lakebed colonised by amphibious plants; (2) P. australis stands covering large parts of the lake area; and (3) wet meadows surrounding the lake area colonised by different Schoenus species. All of the examined amphibious species were found to be mycorrhizal, however terrestrial shoots were more mycorrhizal than aquatic shoots. In the former mycorrhizal frequency F% was up to 100% and mycorrhizal intensity M% up to 67%, while F% was up to 80% and M% up to 16% in the latter. Mycorrhizal colonisation of P. australis with AM and DSE fungi was confirmed in plants growing in different soils and water regimes (17% < F% < 50%; 0.6% < M% < 3%). In the two Schoenus species, F% was up to 99% and M% was up to 14%. According to the literature this is the first detailed report on the presence of AM and DSE mycorrhiza in S. ferrugineus and S. nigricans.

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