Complex urban forest for dense city area

Abstract

Increasing urbanization has destroyed natural areas and detach people from nature, with implications on quality of environment, quality of life, and physical and mental well-being. There is a rising expectation to preserve or create nature-in-city elements to restore healthy urban living. With grave shortage of easily developable land, urban develop-ment in Hong Kong has adopted an ultra-compact form with extensive obliteration of nature. The urban fabric has meagre provision of urban green spaces (UGS) and urban green infrastructure, calling for mitigation by more high-quality UGS. Instead of run-of-the-mill urban park design with manicured landscape, limited vegetation cover and ex-cessive hard paving, some UGS sites can nurture natural vegetation with a complex biomass structure and high leaf area index. The urban woodland offers an innovative option to insert nature into the tight urban matrix and maximize urban biodiversity and ecosystem services. A new development site in Hong Kong, embedded in a dense area, offered the chance to install a pioneering native urban woodland with ecodesign based on urban ecological concepts. It imitat-ed the key traits of the tropical native woodland, including vegetation cover, species diversity, tree density, closed can-opy, interlocking crowns, and vertical stratification. Multiple criteria were used to identify 44 native tree species supple-mented by native shrubs. Besides biomass structure and morphology, constituent ecosystem processes were fostered, such as energy flux, nutrient cycling and food-web formation, with a view to creating a closely-knitted, interdependent and self-sustaining ecological community. The native plants were accompanied by a prepared soil mix with native composition and properties to facilitate woodland establishment. Environmental benefits such as urban biodiversity enhancement, cooling, air cleansing, noise abatement and groundwater recharge would improve with progressive woodland ecosystem succession. The knowledge exchange project tested the scientific methods and furnished experi-ence for similar projects for healthy tropical cities.