Plant community composition on landfill sites after multiple years of ecological restoration

Ecological restoration of closed landfill sites is often challenging due to poor soil structure and seed bank. Currently, the planting mixes used in closed landfills in Hong Kong involved mainly exotic trees with only a small proportion of native trees and shrubs. In this study, we investigated the vegetation regeneration in seven closed landfill sites in Hong Kong. Our Generalised Linear Mixed Models suggested that native plant regeneration, species diversity and evenness were positively influenced by restoration age as well as density and diversity of native species planted. Commonly planted exotic tree species were shown to persist which explained the poorer native regeneration. It is recommended to improve the planting mixes by increasing the proportion of native species. Despite the merit provided by exotic legumes for ecosystem services (e.g. nitrogen fixation), removal of exotic species in the existing plantations is considered necessary to release resources for natural regeneration.