Characteristics of Soil Seed Bank and Tree Regenerations of Riparian Forests in the Upper Reach of Wenyuhe Watershed in Shanxi Province

The soil seed banks of 13 typical riparian forests in the upper reach of the Wenyuhe watershed in Shanxi Province were studied by seed counting and indoor germinations.Seedlings and saplings of tree species were examined.With forest succession,the trend of seed bank,understory regeneration and the tree reproductive strategy were also studied.Seed densities of the 13 communities were between 1290±103 and 3950±154 seeds per square meter,with 63.5% of seeds in the soil layer of 0-5 cm.These seeds belonged to 49 species,which were mainly perennial herbs.There were both seeds of interference-resistant species and typical wetland species.Seed bank similarity index was higher among communities of the same or adjacent succession stage.With forest succession,seed diversity,species number,Shannon-Wiener index,similarity between seed bank and above vegetation all decreased.In the Picea wilsonii forest community of latter succession stage,a large number of P.wilsonii seedling appeared.The seed density of pioneer species Betula platyphylla was the biggest.Betula platyphylla was mainly regenerated by numerous wind-dispersed seeds and fewer sprouts.Because of consumption,there were fewer seeds of P.wilsonii,P.meyeri,Larix principis-rupprechtii and Pinus tabulaeformis,and no viable seeds of Quercus liaotongensis in the soil.Results showed Picea wilsonii,P.meyeri and Pinus tabulaeformis could regenerate by their persistent seedling banks.But there were fewer seedlings and saplings of L.principis-rupprechtii,which only appeared in forest gaps and edges.L.principis-rupprechtii regenerated seasonally.while Q.liaotungensis regenerated by abundant seedlings as well as sprouts.Populus cathayana was regenerated with numerous wind-dispersed seeds and certain vegetative expansion.The results would provide theoretical and technical guidance for the protection and restoration of riparian forests in the Wenyuhe watershed.