Differential degradation of oak (Quercus petraea) leaf litter by litter-decomposing basidiomycetes

Due to production of lignocellulose-degrading enzymes, saprotrophic litter-decomposing basidiomycetes can significantly contribute to the turnover of soil organic matter. The production of lignin and polysaccharide-degrading enzymes and changes in the chemical composition of litter was studied with Marasmius quercophilus, Mycena inclinata and Pholiota lenta, three basidiomycete species typical of oak (Quercus petraea) forests. Within 12 weeks of incubation, M. inclinata decomposed 33%, M. quercophilus 36% and P. lenta 48% of the substrate dry mass. All fungi produced laccase and Mn-peroxidase and none of them produced lignin peroxidase or Mn-independent peroxidases. M. inclinata and M. quercophilus produced considerable laccase activity, while production by P. lenta was low. M. quercophilus and P. lenta produced most Mn-peroxidase at the beginning of the experiment, while the production by M. inclinata was more stable in time. Endo-1,4-beta-xylanase exhibited the highest activity among endooleaving glycosyl hydrolases while 1,4-beta-glucosidase was the main exocleaving enzyme. All fungi decreased the C:N ratio of the litter from 27 to 13-17 and M. inclinata and M. quercophilus also decreased the lignin content. Analytical pyrolysis of decayed litter showed changes in litter composition similar to those caused by white-rot fungi during wood decay, e.g. a decrease in the syringyl/guaiacyl lignin ratio. These changes were more pronounced in M. inclinata and M. quercophilus. The results indicate that different litter-decomposing fungi can cause substantial litter transformation despite considerable differences in the production of lignocellulose-degrading enzymes. (c) 2007 Elsevier Masson SAS. All rights reserved.