Small-scale diversity and succession of fungi in the detritusphere of rye residues.

Transport of litter carbon in the detritusphere might determine fungal abundance and diversity at the small scale. Rye residues were applied to the surface of soil cores with two different water contents and incubated at 10 degrees C for 2 and 12 weeks. Fungal community structure was analysed by constructing clone libraries of 18S rDNA and subsequent sequencing. Litter addition induced fungal succession in the adjacent soil and decreased detectable fungal diversity mainly due to the huge supply of substrates. Ergosterol content and N-acetyl-glucosaminidase activity indicated fungal growth after 2 weeks. Simultaneously, the structure of the fungal community changed, with Mortierellaceae proliferating during the initial phase of litter decomposition. Ergosterol measurements were unable to detect this early fungal growth because Mortierellaceae do not produce ergosterol. In the late phase during decomposition of polymeric substrates, like cellulose and chitin, the fungal community was dominated by Trichocladium asperum. Water content influenced community composition only during the first 2 weeks due to its influence on transport processes in the detritusphere and on competition between fungal species. Our results underline the importance of species identification in understanding decomposition processes in soil.