PRCF forest habitat restoration activities are carried out at sites that have suffered degradation due to conversion into agriculture or because of fire and natural disasters. Forest restoration measures are primarily used at sites where the original natural habitat is desired in order to support endangered species populations, such as for the critically endangered Eastern Black-crested Gibbon in Vietnam. A variety of restoration techniques are used, depending of the condition of the forest land, state of standing vegetation, and cause of degradation. Techniques include natural regeneration, assisted natural regeneration, enrichment planting, and afforestation with native tree species.
Many of the areas we work in on forest rehabilitation retain the potential to regenerate their original forest conditions by just allowing natural regeneration to take place over time. This can be a lengthy process, but the approach is simple and entails just protecting the areas from further anthropogenic disturbance and allowing natural regeneration to take place at its own pace. Notwithstanding, our efforts often involve what we term assisted natural regeneration to help speed up the process of forest restoration, and to support restoration of the forest area with selective species. This, in particular, is the case at the Cao Vit Nature Reserve in northern Vietnam, where the population of this critically endangered gibbon has a very small karst forest area surrounded by village agriculture.
Assisted natural regeneration
Natural regeneration can be enhanced by providing assistance to the surfacing seedlings, saplings, and poles of desired tree species. This is often done by clearing grass and weeds nearby stems and by liberating poles of desired species from vines and other climbers. It is a lengthy and tenuous process that involves a periodical inputs with a great deal of labor over several years until the desired tree species are able to gain strength, ‘shade-out’ weeds, and begin to fill the canopy. Assisted natural regeneration is selective on the species left to grow, but usually only dominant grasses and choking vines are eliminated in the perimeter of emerging trees so that the site vegetation will resemble that of nearby natural forests.
In a number of cases, we engage in enrichment planting, of understory planting with native desired tree species to assist in the forest regeneration process. The activity entails securing and nursing seedlings and willings from desired native species, and thereafter planning these at the target forest regeneration site. Species selected for this process are always native to the area, and in the case of our efforts in Vietnam to restore forest habitat to the Eastern Black-crested Gibbon, we have selected 25 priority species for planting, and 250 secondary species. Priority species comprise those known to be source of food to the endangered gibbon. These are mostly collected as wildlings from the forest, maintained in specialised nurseries, and after several months transplanted to their final locations within the forest restoration site.
When the forestland has been subject to intense pressure where natural or assisted natural regeneration is likely to yield poor results in mimicking the original forest structure and conditions, we engage in afforestation with desired native species. Afforestation techniques usually entail planting of native species in patterns that most mimic the natural forest. Because the purpose is to retain natural forest conditions in as much as possible, we allow for emerging tree seedlings to remain at the target site, and from time to time come back to the site to conduct enrichment planting.