Litter decomposition is an important process for nutrient and organic matter dynamics in forest ecosystem, and influenced by various biotic and abiotic factors. Ltter quality such as nitrogen and lignin contents is one of the important indicators to understand the difference of pattern and rate in the litter decomposition among different vegetation in forest ecosystem of northern Hokkaido, Japan. However, the pattern and rate in Sasa litter decomposition, their difference with the tree litter and their relations to the litter chemical property has not been clarified yet. Therefore, we investigated the litter decomposition process and litter chemical qualities of Sasa leaf, culm and tree leaf litters for 3 years using the litterbag method in natural cool-temperate mixed forest of Hokkaido University ’s Nakagawa experimental forest, northern Japan.
  In initial litter quality, nitrogen concentration of Sasa culm was significantly lower than Sasa leaf and tree leaf litters. Lignin concentration in Sasa culm was lower than that in tree leaf. Silicon concentration in Sasa leaf was higher than that in Sasa culm litters were significantly lower than that in tree leaf litter, suggesting that the high silicon content in Sasa leaf and low nitrogen content in Sasa culm were important decreasing factors as a recalcitrant material of the litter decomposition for each litter compared with tree leaf litter.
  Decomposition rate of each litter became slower in the 2nd and 3rd –year than that during the 1 year with the increase of nitrogen concentration in each litter. In particularly, the decreasing of litter decomposition and the increasing of nitrogen concentration in 2nd and 3rd year was remarkable in the tree leaf litter compared to the Sasa leaf and culm litters. It was suggested that the high lignin and nitrogen content in the initial litter of tree leaf decreased the litter decomposition rate in the later period due to the inhibition of lignin breakdown by the higher nitrogen content. This study indicated that difference of the litter decomposition rate and patter of Sasa leaf and culm litters compared with the tree leaf was explained by the difference of the initial contents of silicon, nitrogen and lignin in each litter.