The effect of forest tree species change on decomposer diversity :A case study of the Breuil research site (Burgundy, France)

Microbial diversity and its relation to decomposition activity were studied in forest soils. An optimized fingerprinting method of TGGE (temperature gradient gel electrophoresis) was used to determine the patterns mainly of fungal but also of bacterial communities during decomposition of different substrates (cellulose, wood, tree litters) in a native forest and four monocultures . The diversity data were compared to measurements of decomposition rate in the samples (plus cellulase activity, fungal biomass and C/N ). Further, effect of environmental variables (soil chemistry, moisture and temperature) to diversity was also targeted. Substitution of tree species caused changes in the composition of fungal and bacterial communities. Similarly, the communities were changing during the incubation period. However, any significant decrease of species richness was detected for any substrate or tree species. The differences in the decomposition rate did not seem to be influenced by a species loss or community change, but rather by a change in the microclimatic and nutrient conditions, influencing biotic interactions and/or species activity. Leaf-needle mixed litters sustained fungal diversity and increased the decomposition rate. During summer, species richness tended to decrease and common species were replaced by infrequent ones, able to tolerate dry conditions and to be very active.