Species adoption for sustainable forestry in Hong Kong’s degraded countryside

Abstract

Intensively urbanized Hong Kong has a degraded countryside envelope with 170 years of afforestation history. This study assessed seedling quantity, species composition, native-exotic relativity, and native ecological traits in 30 years. Data were analysed by cluster analysis, two-way indicator species analysis (TWINSPAN), and principal component analysis (PCA). The plantations received 16.54 million seedlings from 209 species. Seedling profile skewed towards 142 native species (67.9%) and 9.49 million exotic seedlings (57.4%). The dominant species group had three exotic species each with >1 million seedlings. The abundant group of 27 species had contained 19 natives associated with main primary forest components. The 179 species in frequent and rare groups denoted changing and diverse species selection. Analysis of start and truncation times found 50% of natives with ascending trend and 33% of exotics with descending trend. Aggregate ecological value of natives increased progressively. TWINSPAN classified native species into two groups with signature characteristics. PCA revealed scattered distribution of natives by adoption trend, start time, truncation time, and ecological value. Ecological restoration of synergistic-mutualistic associations between native plants and wildlife has gained importance. Potential pioneer and enrichment-planting arboreal species were identified to sustain the afforestation programme. Hong Kong has a rich vascular flora with about 390 native tree species, implying that around 250 native tree species had never been used in afforestation. Large-scale planting trials should be conducted to further refine species choice in future afforestation. The findings could inform afforestation and conservation efforts in Hong Kong and other degraded tropical lands.