Mineralization of cellulose in the presence of chitin and assemblages of microflora and fauna in soil.

Nitrogen content is an important factor controlling decomposition of resistant substrates. We examined the decomposition of purified cellulose in the presence of a structurally similar, resistant organic N compound, chitin. Carbon-14-labelled cellulose was added to sterile ari-dried sandy loam soil in flasks, half of which were also amended with purified chitin. Grassland soil organisms-a fungus (Fusarium oxysporum) or a bacterium (Flavobacterium sp.) with or without their respective nematode grazers (Aphelenchus avenae or Pelodera sp.) were added to the substrateamended soils, and decomposition was monitored by carbon dioxide evolution and NH 4+ -N mineralization. More 14CO2 was evolved and at a higher rate from the fungal treatment than from the bacterial treatment. Grazing enhanced 14CO2 and total CO2 evolution and NH 4+ -N mineralization in the bacterial treatments and NH 4+ -N mineralization in the fungal treatments. Nitrogen was mineralized both from native organic sources and from chitin. The addition of chitin did not enhance and, in most cases, decreased cellulose decomposition.