Seed rain and seedling survival are major factors limiting vegetation regeneration on rehabilitated quarries

To evaluate factors limiting vegetation regeneration, studies of seed rain, seedling emergence, and survival were carried out on different phases of three different-aged quarries in Hong Kong. Seed-rain results showed that 1,741 seeds from 35 woody species were collected from 160 traps in a 1-year period. Older sites had higher seed number and species than younger sites. In terms of number, 68 % of seeds were dispersed by birds, whereas 30 and 2 % were dispersed by wind and civets, respectively. In situ seedling emergence experiment showed that most of the 12 woody species had higher emergence under field conditions, which implied that seedling emergence was not a limitation of vegetation regeneration. Most emergent seedlings finally died, which had significant correlations with the adverse microhabitat conditions. It was concluded that although seed rain contained some native woody species, it may still be insufficient in order to accelerate natural vegetation regeneration at the later successional stages on our local quarries. Management strategies should take into account the possibility of enhancing seed dispersal and improving microhabitat conditions. Using native species with fleshy fruits to attract birds by enrichment planting is strongly recommended, and postplanting care is essential to quality development of the rehabilitated ecosystem.