Clarification of Factors Inhibiting Regeneration of Glehn's spruce (Picea glehnii) at the Initial Stage of Natural Regeneration

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Research was conducted on factors preventing natural regeneration of the Glehn's spruce (Picea glehnii) at early stages of growth, such as fungi, field mouse, moisture in forest floor and photoenvironment. Analysis of the environment where natural seedlings grow was also conducted.Six species of filamentous fungi were separated from Glehn's spruce seeds which had passed the winter under the forest floor. Among those, Racodium therryanum, which rotted the seeds, and Rhizoctonia solani and Fusarium rosume, which dumping-off the seedlings, are the significant types of fungi. While seeds are often eaten by fiels mouse in forest thicks with Sasa, the number of seeds eaten decreased on bare land where the ground had become exposed due to surface scraping. By removing Sasa by surface scraping, the activity of field mouse was limited and the survival rate of seeds was jmproved. Regarding the seasonal changes of water content in the soil, it changed sharply in the L layer, from 10 to 70%. It was found that seeds above the L layer were prone to dehydrate and die. As for photoenvironment, it was found that more than 30% relative illumination was necessary for sufficient growth of seedlings and planted Glehn's spruce trees. Natural seedlings of the Glehn's spruce grow on mossy forest floors, fallen trees, mounds, stumps and bare land. Surface scraping of small areas in the forest is thought to be effective for hastening natural regeneration.