Seasonal Dynamics in Forest Soil Seed Banks along an Elevational Gradient in the Rocky Mountainous Area of North China

Although exploring soil seed bank characteristics and dynamics is conducive to plant diversity protection and restoration, few investigations have been undertaken in the rocky mountainous area of North China. To address this research gap, qualitative and quantitative changes in soil seed bank characteristics over different seasons and elevations as well as potential causes for differences were examined, using data from 25 secondary forest communities in the Songshan area of Beijing, China. Nonmetric multidimensional scaling (NMDS) was used to test the similarity of the composition of the seed bank and the understory vegetation during different seasons. In addition, the structural equation model (SEM) was used to explore the direct and indirect effects on seed bank density. The results indicate that abundance and species richness decreased with elevation, with seed density reaching its maximum and minimum levels in April and July at all elevation levels, respectively. In terms of species composition, the understory vegetation was significantly different from the seed bank, and the proportion of herbaceous plants species in the seed bank was higher. Soil total nitrogen, available phosphorus and available potassium all changed with elevation, directly or indirectly affecting seed bank density. The application of seed banks present in topsoil from the rocky mountainous area of North China can be potentially used for ecological restoration. It is important, however, to consider the elevation and the season related to the removal of the topsoil to achieve optimal effects