Colonization of woody seedlings in the understory of actively and passively restored tropical moist forests

The status of woody seedling colonization gives clues about the self-sustainability of restored forests, a tenet of restoration success. Little is known about woody seedling colonization in restored afrotropical forests. We evaluated effects of restoration methods (active vs. passive), sampling year, restoration age, and distance from old-growth forests on seedling colonization in restored afrotropical moist forests. Seedlings were measured in 2011 and 2014 in 71 clusters of 284 permanent sampling plots (12.6 m(2) each) in actively (initially 3-16 years old) and 21 clusters of 63 plots in passively restored forests (initially 16 years old) in Kibale National Park, western Uganda. Seedlings were also measured in nearby old-growth forests in three clusters of five plots in 2014. We determined species diversity, richness, abundance per plot, and species composition as measures of seedling colonization in restored and old-growth forests. We found that diversity, richness, and abundance of seedlings were significantly higher in passively than actively restored forests. Diversity and richness but not abundance significantly increased between sampling years and with restoration age. Distance from old-growth forests did not significantly affect diversity, richness, and abundance. Species composition of actively and passively restored forests was different from that of old-growth forests after 19 years since restoration started. Our results show that passive restoration should be the preferred method for recovering afrotropical forests, and highlight the effect of continued management on biodiversity of restored forests.