The Seed Bank in Logging Gaps in Populus davidiana-Betula platyphylla Secondary Forests in Changbai Mountain

The soil seed bank in logging gaps of different sizes and ages was studied in Populus davidiana-Betula platyphylla secondary forests in Changbai Mountain.The result showed:There were significantly fewer seeds in gaps than under canopy although the species diversity in gaps was greater than under canopy.The soil seed bank reserves had significant difference in magnitude among gaps of different sizes and ages.The reserve decreased and the species diversity increased with the increasing gap age,and the largest reserve occured in the gap size of 50～100 m2.There was big variation of the seed distribution in different site within gaps.The seed bank magnitude was mainly decided by seeds in humus layer(0～10 cm)at the initial stages of gap,seeds in the litter contributed more and more to total seed bank with increasing gap age due to retardarce from the litter.The dominant species in the seed bank in gaps were mainly composed of Fraxinus mandshurica,Tilia amurensis,Maackia amurensis and Acer mono,which accounted for 74.3% of total seed numbers.In addition,there was low similarity in species composition between seed bank and seedlings within gaps.