Litter quality, decomposition rates and saprotrophic mycoflora in Fallopia japonica (Houtt.) Ronse Decraene and in adjacent native grassland vegetation

Fallopia japonica succeeds in invading different ecosystems likely because of its huge biomass production. This biomass is characterized by low nutritional quality and low decomposition rates but knowledge on whether these features are correlated to microbial decomposers is still lacking. The aims of this work were: i) to determine litter decomposition rates of native grassland vegetation and F. japonica under different conditions in a year-round experiment; ii) to evaluate litter quality and/or site effect on the decomposition of the invader and native vegetation and iii) to characterize mycoflora isolated from F. japonica and native vegetation litter. The results showed that F. japonica litter decomposes 3-4 times slower than that of native grassland, mainly due to its low N content and consequently high C/N ratio both in leaves and stems. As decomposition proceeds C/N in F. japonica litter decreases to values approaching those of the grassland litter. Site had no effect on the decomposition rates of F. japonica and grassland litter. Total fungal load and composition differed between F. japonica and native litter, and also varied across sites. These results indicate that the successful invasive plant F. japonica affects the structure and functions of the invaded ecosystem through a huge production of low quality, slow-decomposing litter that selects saprotrophic fungi.