Tree seed predation on degraded hillsides in Hong Kong

Abstract

Hong Kong was once entirely covered in subtropical rain forest but almost all of this had been cleared by the 17th century. Today around 9% of the land area is covered by secondary forest mostly developed since 1945 with an additional 5% under plantations, largely of exotic species. The use of mixed, native species for reforestation has only started recently. The aim of this study was to determine whether seed predation was a barrier to natural forest regeneration on degraded hillsides. Removal of seeds of eight tree species in the winter of 1995 and 12 in 1996 at four Hong Kong hillside sites was monitored. Seed removal at the two shrubland sites was higher than at the two grassland sites in both 1995 and 1996. Most seeds placed in the shrubland sites in 1996 were removed, 11 of 12 species were totally removed from one shrubland site within 60 days, while only one of 12 species was totally removed in one grassland site. Rats were found to be the major seed predator. They included Niviventer fulvescens and Rattus rattus flavipectus. The tough/thick coated seeds of Choerospondias axillaris and Elaeocarpus sylvestris had the lowest mean percentage removal. Currently, all reforestation efforts in Hong Kong use container-grown seedlings, which is expensive even on accessible sites and impractical in remote areas. The results of this study suggest that direct seeding may be possible if species with tough/thick coated seeds are used.