A field assessment of a 18-year old native tree reforestation site in Hong Kong

Abstract

The current Hong Kong reforestations were using the exotic species which may harm the development of native species. Although the proportion of native species was increasing, the reforestation will all native species still did not perform in Hong Kong countryside. Thus, the experimental plantation with all native species was set and investigate its growth with evaluating its growth. This reforestation experiment with all native species was done in a subtropical site in Hung Lung Hang, locating in Hong Kong. Enrichment planting with container-grown seedling were applied in the site. A closed-canopy forest was formed 18-years after the start of plantation. This study investigated the 18-year reforestation work with all native species. The tree growth data with survival, stem height and diameter at breast height (DBH) in the plantation was surveyed. Together with the previous survey data, a set of monitoring data was set to analysis. Then, number of survivals in each species, the mean stem height for each species and the mean DBH for each species were regressed into rate of change of survival rate, growth rate in stem height and growth rate in DBH respectively. Together with the relative height increasement (RHI) for comparing the species mean initial stem height H1 and species mean final stem heights H2 to calculate the species mean growth, the growth of each species was evaluated. The species were evaluated with the growth and survival rate. The site trees community is referred to the species diversity with Shannon index and the basal area of all the trees in a unit area. The basal area of all the trees in a unit area with DBH of all the trees in the site and the site size in area. For the tree growth in the site, the indicators for the growth showed the common result. Then, the tree growth and survival were used to categorize the species in different life strategies. The strategies can be categorized into fast growing, high survival and balanced. Species in the site showed the strength in different category. Aporusa dioica, Cyclobalanopsis edithiae and Viburnum odoratissimum with shade tolerance are grew with high survival rate. Choerospondias axillaris, Mallotus paniculatus and Cordia dichotoma are found with high growth rate, while C. axillaris and M. paniculatus are able to be planted as the pioneer species. The species with balanced high growth and survival performance is also found from Cyclobalanopsis edithiae. In terms of the whole plantation, the result showed a positive outcome for the development and growth of whole plantation. The overall situation of the trees is high survival. The previous exotic plantations were survived with 20% survival rate, but this plantation was surviving with over 30% survival rate. Moreover, the planted trees in the site showed a high performance when compare with the previous exotic plantation in Hong Kong in terms of tree species diversity and natural regeneration. The species diversity was high with Shannon index: 2.48 (focused on trees in planted species). These parameters are important to create an environmental forest for the ecology conservation. The result of reforestation with native species is justified with the justification for the current reforestation in Hong Kong, which is protecting the biodiversity and ecological restoration. The plantation with native species should be further promoted for the ecological protection in the countryside.