Seedling demography and establishment of Cryptomeria japonica in a cool- temperate, old-growth, conifer hardwood forest in the snowy region of Japan

摘要

To clarify the establishment pattern of Cryptomeria japonica seedlings, the demography of current-year seedlings was studied under various micro-environmental conditions for 2 years in a cool-temperate old-growth forest in the snowy region of Japan. In both years, more than 70% of seedlings that emerged died within a year, and differences in the survival rate of seedlings with respect to micro-environmental conditions were similar. While a number of seedlings survived at the sites on fallen logs andin mineral soil, almost no seedlings survived at the sites with either broad-leaved or coniferous litters at the end of the first growing season. The negative litter effect may kill most small seedlings of C, japonica. In addition, we found that survivalrates of the seedlings were greater as the distance from the nearest adult and canopy openness increased. An analysis using Quantification Theory I showed that, of the possible micro-environmental factors, substrate conditions had the strongest effect on the survival of seedlings. The analysis also indicated that distance from the nearest adult and canopy openness also affected seedling survival significantly and to almost the same extent, although the effects were weaker than those for the substrate condition. Given the limited establishment sites for C. japonica seedlings, layering is suggested to be the main mode of regeneration in this forest.