Biodiversity and Quality of Cultivated Trees in Domestic Gardens of Hong Kong

Abstract

Domestic gardens, constituting an important component of the urban green infrastructure, can enrich urban biodiversity in a unique way. This study evaluated species composition, floristic diversity, amenity-ecological characteristics, habitat condition, and performance of trees in domestic gardens. The garden-city estate in urban Hong Kong has European-style detached houses built in the 1920s. The 1,501 individual trees belonged to 72 species, 61 genera and 36 families. With domination by a small cohort of popular species, they skewed heavily towards exotic species count (84.7%) and tree count (91.3%). The prominent amenity-ecological attributes were fast growth and establishment, and interesting tree form and foliage. Nonmetric Multidimensional Scaling indicated strong association between species distribution in domestic gardens and habitat-tree variables such as tree density, tree aggregation, species aggregation, lots with trees and house lots. Redundancy Analysis (RDA) showed correlation (p<0.05) between tree and species counts and lot frontage and garden depth. Detrended Correspondence Analysis identified 16 species with widespread moderate or severe structural damage, and 22 species with very poor or poor overall condition. RDA further found correlation (p<0.05) between structural damage and overall condition, and tree position and confinement type. An integrated landscape plan with appropriate incentives and technical guidance can further augment arboreal biodiversity. Management implications for conservation and planting of garden trees could be applied to south China and other cities.