Natural regeneration condition in Pinus koraiensis broad-leaved mixed forest

The Korean pine (Pinus koraiensis) broadleaved mixed forest was one of the dominant vegetation types in Changbai Mountain Forests,now it is a rare remnant ecosystem with an irreplaceable reference for understanding the pre logging environment of the region. Primary objective of this study was to examine the natural regeneration of Korean pine in the forest and its relation to the forest composition and structure. Our results indicated that natural regeneration was closely related to forest community composition, structure and human disturbances such as pine seeds harvesting. Natural regeneration of the Korean pine was moderate in the Mongolian oak Korean pine forest on steep slopes, where the canopy density reaches 80%～90% or more and the proportion of Korean pine in the forest was high. Over ten thousand seedlings and small saplings of Korean pine per hectare were observed, but they rarely grew up under close canopies. In Korean pine broadleaved mixed forests there is no much natural regeneration of conifer trees including Korean pine, except in the relatively close canopies. In the Korean pine broadleaved mixed forests the natural regeneration is largely of hardwood trees, especially seedlings and saplings of Fraxinus mandshurica, which sometimes reach more than 13000 plants per hectare. At higher elevations the amount of spruce and fire seedlings and saplings increases. A significant low density of seedlings at the old partially cutting sites was observed, which suggested that partial removals of canopy trees strongly influenced regeneration. Our results also showed that seventy four per cent of the seedlings and saplings of shade tolerant species was recorded under the canopy. Interestingly, more than 70% of total natural regeneration of Korean pine was found within 2.5 m from the standing live trees, which is the average radius of crown projection. Therefore, the best seedling regeneration environment of Korean pine and the shade tolerant species is under the close canopies.