Evaluation of regeneration potential of Pinus koraiensis in mixed pine-hardwood forests in the Xiao Xing’an Mountains, China

Abstract

Large scale harvest of Korean pine (Pinus koraiensis) seeds as a food product in the mixed Korean pine-hardwood forest of northeastern China poses a serious threat to the sustainability and restoration of this endangered regional ecosystem. Seed collection over past decades greatly reduced the seed bank and subsequent seedling and sapling recruitment, and impacting a wide array of granivorous animals that rely on the pine seeds. We surveyed Korean pine seeds, including solid seeds (SS), insect consumed seeds (ICS) and other (animal) consumed (OCS) kernels, of the seed bank (forest floor and the top 10 cm of mineral soil), the seedlings and saplings from 1 m2 sample plots in five forest types in Liangshui Nature Reserve (LNR) of the southern Xiao Xing’an Mountains in northeastern China to provide accurate information for assessing the Korean pine regeneration potential. The average number of pine seeds in the seed bank were 11.2 seeds/m2, 9.1 seeds/m2, 4.6 seeds/m2, 1.1 seeds/m2, and 0.2 seeds/m2 in Korean pine-basswood forest, mixed Korean pine-hardwood forest, mixed conifer-hardwood forest, white birch forests, and oak forests, respectively. In the first three forest types, percentages of SS (potentially viable seeds) were 11.2%, 3.5% and 27.8%, respectively. The percentages of ICS (not viable seeds) were consistent at around 35%. The higher but variable percentages of OCS (not viable seeds) indicated high seed predation in these forests. Compared with other studies, we recorded higher percentages of seed damage, probably due to our survey approach and the increased depth of seed bank sampled in our study. Depletion of pine seeds in the seed bank greatly reduced seedling and sapling recruitment. Densities of pine seedlings varied from about 180 trees/ha in the mixed Korean pine-hardwood forest to about 5,400 trees/ha in the mixed conifer-hardwood forests and showed a high degree of spatial variation. Saplings were rare in the mixed Korean pine-hardwood forest, but ranged in the thousands in other forests. Large scale pine seed harvest has seriously threatened the sustainability of the mixed Korean pine-hardwood forest ecosystem. Scaling down the seed harvest or supplemental planting of pine saplings are urgently needed to maintain the health of the existing Korean pine forests and to restore this endangered ecosystem.