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Ecological changes in soil covers were studied in terms of physical, chemical and biological properties in the three quarries. Results show that all soils were classified as sand loam in texture, and high bulk density and low total porosity were common problems. Soils were strongly acidic to moderately acidic in reaction. Organic C, total N, extractable NO3 - and extractable cations increased with increasing rehabilitation age, but others did not show similar trends. The results of mineral N flux in soil show that ammonification predominated over nitrification in TH and LT, while nitrification predominated in SO in wet season. In dry season, ammonification predominated over nitrification in all phases, except TH. Net N mineralization increased with age. The results of soil microbial study show that older sites had the highest total microbial abundance and biomass C and N, while those in younger sites were low. Metabolic abilities of soil microbes developed gradually with ages in SO, but TH and LT had the similar patterns of carbon source utilization. The group of G- bacteria dominated in all sites, in which cy19:0 represented more than 15% of the total extracted FAMEs. The group of fungi and AM fungi decreased with increasing ages in the three quarries.Lacks of seed rain and seed bank were major factors limiting vegetation regeneration. Physical and chemical problems of cover soils are still severe even after 10 years of rehabilitation. Therefore, adding native species with fleshy fruits to attract birds, and leguminous species to assist in the buildup of nitrogen capital should be recommended. Application of organic composts should be considered by quarry contractors and managers during early rehabilitation period to improve soil structure and raise nutrient storage capacities.To evaluate the ecological succession in the floristic composition and structure of closed quarries, studies of the current vegetation development and seed dynamics were carried out in the three quarries, namely Turret Hill Quarry (TH), Lam Tei Quarry (LT) and Shek O Quarry (SO). The floristic composition shows that the species richness and Shannon index were higher on older phases than other younger phases in the overstorey and understorey vegetation. Although planted exotic species dominated the overstorey at different phases, some native species became more dominant in the understorey, and the importance value of native species accounted for more than 50%. Seed rain results show that older sites had higher seed number and seed species than younger sites. In terms of number of seeds, half were dispersed by birds, while 23% and 27% were dispersed by wind and civets, respectively. Seed germination experiment shows that most species from all twelve woody species had higher germination in SO, though most emerging seedlings finally died under the field condition. In the soil seed bank study, high seed species and density were recorded on older sites. Non-woody species predominated on all phases of the three quarries, but some pioneer tree and shrub species were better represented on older sites.Zhang, Hao.Adviser: L.M. Chu.Source: Dissertation Abstracts International, Volume: 73-02, Section: B, page: .Thesis (Ph.D.)--Chinese University of Hong Kong, 2010.Includes bibliographical references (leaves 238-280).Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [201-] System requirements: Adobe Acrobat Reader. Available via World Wide Web.Abstract also in Chinese