Restoration of Native Ecosystems
Native Tree Nursery and Forest Restoration at Hong Kong and South China
The Flora Conservation Department of KFBG has been active in forest restoration by providing native tree seedlings for re-greening disturbed sites and enriching secondary forest in Hong Kong. Our Native Tree Nursery (NTN) was established in 1997. It aims to produce seedlings of native tree species of local provenance that are particularly suitable for ecological restoration. Every year, we produce more than 25,000 seedlings that are mainly supplied to local NGOs that are active in forest restoration of Hong Kong.
The seeds we use are collected in Hong Kong with the permission of the Agriculture, Fisheries and Conservation Department of the Hong Kong Government. In order to ensure the ecological value of the restored forest and the genetic health of the planted forest species, we aim for a diverse collection of 50–100 tree/shrub species sourced from a wide range of source populations within Hong Kong.
To reduce the impact of our operations on the environment, we use only minimal amounts of organic fertiliser and we don’t use any herbicide at all in our Native Tree Nursery operation. Any weeds are manually removed from pots in the nursery.
In the selection of species, we follow the framework species approach by emphasizing tree species that are dominant in local native forest and species that are attractive to local wildlife. Examples of native species that we routinely use include Garcinia oblongifolia, a widespread native tree that can be found in lowland forest and shrubland. Its produces yellow fruit that is edible to wildlife as well as to humans. Another example, Elaeocarpus spp., is a group of up to six evergreen tree species distributed in shrubland, lowland and upland forest of Hong Kong. They produce bluish to green drupes that are a favourite food of local wildlife.
Outside Hong Kong, the Flora Conservation Department also helped in the establishment of native tree nurseries at Bawangling National Nature Reserve in Hainan to provide native tree seedlings needed to restore the forest habitat of the critically endangered Hainan Gibbon.
Restoration and Enrichment of the KFBG Woodland
The barren hillside in 1950-60s (top) and the luxuriant forest
in 2014 (bottom).
The hillside of KFBG has been developed from an almost barren ravine in the 1950–60s, into what is nowadays a mosaic of secondary native woodland, exotic plantations, and farmland lots, intersected by roads and paths. These woodlands are now an important habitat for wildlife and a hotspot for animal sightings.
A number of orchard terraces became unproductive and so were abandoned several years ago.
The Flora Conservation Department is now planning to convert the patchy mosaic of abandoned orchards into new woodlands of native tree species, including fruit trees, to enrich the species diversity and ecological value to wildlife, and to link up existing natural forest patches. Selective thinning and removal of the orchard trees will be carried out in stages over many years. Native tree seedlings provided by our Native Tree Nursery will be planted at the site. The planting scheme of the forest restoration work will be planned based on vegetation survey of other Hong Kong forests. Wood from the orchard trees will be recycled as mulch and biochar to enhance the soil on the terraces which has become depleted by decades of orchard mono-cropping.
Enhancement of Exotic Plantations to Increase Ecological Value
KFBG Native Tree Nursery
Extensive areas of exotic plantation were established in Hong Kong between the 1950s and 1990s for the purposes of soil erosion control and landscape integration. While these plantations of mainly Acacia spp. and Lophostemon confertus have served these intended purposes, it is now widely recognised that they are of very low ecological value to native wildlife. In addition, these exotic trees are invasive, and, impede the natural development and recovery of native forest by excluding bird species, which are major seed dispersal agents of most native tree species. Such areas of exotic plantation are therefore often referred to as “green desert”.
The Flora Conservation Department hopes to improve this situation by proposing enhancement of the exotic plantations in Hong Kong with native tree species and to raise the ecological value to wildlife. This will be achieved by gradual removal of the exotic trees and filling in with native tree seedlings. Eventually, we plan to completely replace the exotic trees with a diverse mix of native tree species.
We will start such work at an experimental scale in KFBG, and hope that it will be extended to exotic plantations in Hong Kong. We appreciate that each tree is a living being in its own right and will only remove trees when absolutely necessary, though we recognise that acacias are very invasive and many are old and nearing the end of their natural life anyway. The native species we choose to plant in place of the removed exotic species in the forest will be selected with the framework species approach by emphasising dominant native tree species that are attractive to native wildlife as habitat or fruit source. Such species will attract wildlife that will then bring seeds of other plant species to the site and speed up the process of natural recovery of the forest. We hope that the restoration work we conduct can be developed into a model that will have wider application in the region.
Invasive Alien Survey and Eradication
Alien invasive species are widely recognised as one of the biggest threats to global biodiversity. Alien species are introduced either unwittingly or deliberately for various purposes. While most of the introduced species may not survive in the local environment, a few of them may be able to thrive, naturalise and become a threat to the native plant species.
Like many places in Hong Kong, KFBG is under threat of invasion by alien species including Mikania micrantha and Lantana camara. To understand the threat posed by invasive species at KFBG, we have conducted a survey of invasive species in our wild areas, and have found that in addition to the two species mentioned above, ornamental species such as Begonia wallichiana, Begonia cucullata and Neomarica gracilis are also important alien invasive species on our site. To cope with the situation, we have started eradication programmes for Mikania micrantha, Begonia wallichiana and Begonia cucullata, thanks to the efforts of our frontline staff and volunteers. Similar programmes will be extended in the future to other alien invasive species.