Response of Quercus robur L. seedlings to north-south asymmetry of light within gaps in floodplain forests of Slovenia

摘要

To examine Quercus robur establishment and growth in low to intermediate light levels, we analysed regeneration in different microsites created by light asymmetry within gaps in two main floodplain forest regions of Slovenia: Dolinsko and Krakovo. Four years after a mast year in 1995, we installed systematic grids of 1x1 m plots in 11 gaps (0.03-0.40 ha) on wet and dry site variants. In 256 plots, seedling species, cover, density, height, height increment, browsing damage, tree architecture, understory vegetation species and cover, and direct and diffuse light were measured. The average seedling density in all gaps was 15/m~2, but the highest densities were found in gap positions with low diffuse light levels (10-20%). Competing understory vegetation was more abundant in positions with high diffuse light. In gaps on dry site variants a combination of low diffuse and high direct light was favourable for regeneration. The results indicated that Q. robur can successfully establish in gaps. Here, bothlight components were sources of within gap resource heterogeneity, therefore knowledge of light asymmetry can improve regeneration success.