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The effect of temperature on the sporulation of aquatic hyphomycetes associated with decomposing oak (Quercus robur L.) leaves

2011The effect of temperature on the sporulation of aquatic hyphomycetes associated with decomposing oak (Quercus robur L.) leaves.KEBEDE Yared (Ethiopia)
Organisation:University of Coimbra, Coimbra (PT) - Mount Allison University (Canada)Supervisor :Cristina Canhoto (UC) & Felix Barlocher (MAL)
Summary: Temperature is the main factor that controls the colonization, succession, distribution, growth and sporulation of aquatic hyphomycetes associated with leaf decomposition in streams. Disturbance induced by global warming has been affecting these biological processes. In this study, we addressed the effect of temperature (5, 10, 15 and 20oC) on the sporulation of fungal communities developing in oak (Quercus robur L.) leaves immersed in a low order stream by periodically sampling the litter bags for 12 weeks. Decomposition proceed at a rate of 0.006 day-1 which resulted in a 40% of mass loss in 84 days. All leaf quality parameters except nitrogen significantly decreased through time. Fungal biomass and sporulation followed a similar pattern characterized a rapid increase to a peak between day 28 and 42. The sporulation rate was significantly determined by incubation temperature with the highest sporulation achieved at 15oC. At later stages of decomposition, species achieved higher sporulation at 10 and 5oC. A total of 26 species of aquatic hyphomycetes were identified from the leaf samples but species richness was not affected by temperature. The oveall fungal activity was defined by the dominant species Tetrachaetum elegans, Clavariposis aquatica, Alatospora acuminata, Articulospora tetracladia and Mycocentrospora acerina. However, most of the sampling dates were characterized by medium diversity and evenness and the cluster analysis effectively discriminated the abundance of early colonizers from the remaining sampling dates. The simple model also described the field observed pattern of mass loss. The overall response of the species to temperature oscillation was represented by a concave curve as evidenced by successive increase in sporulation towards the optimum (15oC) followed by a decline. Therefore, litter decomposition studies based on expected increase in mean water temperature should consider temperature oscillation and the response curves (Jensen’s inequality) to avoid misleading results.