Leaf Litter Decomposition Differences between Alien and Native Maple Species

This paper presents a comparative analysis of the leaf litter decomposition of two alien (Acer negundo, A. pseudoplatanus) and one native (A. platanoides) maple species. The leaf litter fall of Acer pseudoplatanus was collected in the Girionys Park, situated in the south-west of Kaunas, and leaves of A. platanoides and A. negundo were collected in the Santaka park, located in the eastern part of Kaunas in the autumn of 2008. A laboratory incubation experiment was conducted to evaluate the effect of alien and native maple species on ecosystem functioning, the response of microbial transformations and decomposition of maple litter. The study quantified the amount of CO2 evolved from the decaying litters and the population of fungi, bacteria associated with the soil in forests under decomposing leaves. Decomposition of maple leaf litter was studied under laboratory conditions using the respiration technique. Chemical composition of the litters was determined before incubation by the dry combustion method. The decay rate of the maple litters varied significantly between species. Acer negundo litter decayed more rapidly (K-w = 0.003488) than A. platanoides (K-w = 0.002046) or A. pseudoplatanus (K-w = 0.00166). This variation in decomposition rate corresponded with indicators of litter quality (C/N ratio, N and C) with decomposition mostly being explained by C content. The CO2 evolution differed significantly between the species; it was considerably higher in alien A. negundo litter. Bacteria and fungi quantities varied in soil associated with the three maple species. Microbial populations were similar in the soils associated with A. platanoides and A. negundo, while densities were lower on the site associated with A. pseudoplatanus. CO2 evolution was positively correlated with the number of fungi and bacteria in the soil under maple litter. The leaves of A. negundo showed the fastest decomposition rate, and it is likely that faster nutrient cycling will occur in the soil where A. negundo grows and provides evidence how invasive species may alter the functioning of forest systems.