|
Forest classifications would indicate which areas require intervention to improve their protective or production functions. The classification could also indicate which have especially high biodiversity value. This may be useful in formulating regional landuse plans |
Plantation forestry and farm forestry are not the only ways in which reforestation may occur and, in many cases, regrowth via natural successional processes will be the means by which many extensive areas of degraded land are most likely to become reforested.
Recovery will often depend on preventing disturbances such as fire, which can be a major challenge. Nonetheless, such regrowth is now common across the region. The areas of land involved are large, although statistics on just how large these areas might be are difficult to gather.
These so-called "secondary forests" were once viewed as "wastelands", but there is now much wider recognition that many secondary forests are still very valuable (and should be more properly seen as "regenerating" forests).
Many contain species that are able to provide valuable timber and non-timber products (although it may take some time before harvesting can occur once more), and many provide important habitats for wildlife.
Most are also important because of their role in protecting watersheds. Provided further disturbances such as fire or additional logging are controlled, these secondary forests have the capacity to continue providing these benefits well into the future.
Not all secondary forests are the same, and their composition and structure vary according to their historical origins and management regimes (e.g. those created by heavy logging differ from those developed after agricultural disturbances).
Better ways are needed for grouping these forests into either productivity classes (i.e. for economic purposes), functional types (for watershed purposes) or successional stages (for biodiversity purposes). Some work on this process has already been initiated (Chokkalingam et al. 2001).
Such classifications would indicate which areas require intervention to improve their protective or production functions. The classification could also indicate which have especially high biodiversity values. This may be useful in formulating regional landuse plans.
The capacity for successional development and natural recovery to take place in these secondary forests will vary with the intensity of the previous disturbances, and the capacity of trees from nearby undisturbed forests to reach and colonise the secondary forests.
|
Box 6. Contrasting approaches to enrichment planting in Malaysia Experimental enrichment planting has been carried out over 10 000 ha of logged-over forest in Sabah. The approach currently being used has evolved over time and many changes have occurred as experience has accumulated. Initially, trees were planted at 3 m spacings in rows that were 10 m apart. The planting row was cut as a 2 m wide strip through the forest, and weeding was undertaken following the planting of seedlings. The seedlings planted in Sabah were mostly wildlings. Over time changes have occurred in the technique, most especially in the extent of climber cutting. There has also been increasing attention paid to tending weeds around naturally occurring seedlings of commercially attractive species. Weeding can continue for up to six years after enrichment. Results so far have been promising, although the economics of the operations have been enhanced by payments made for the carbon sequestration taking place as the forest recovers. A different approach is being developed in Peninsular Malaysia. This is because these forests have a larger number of big canopy trees remaining than is the case in Sabah. This has made enrichment more difficult because the overstorey shade has slowed seedling growth rates. Traditional line planting methods have been used, but an approach being tested now uses taller seedlings (up to 2 m height) planted in holes dug by a Bobcat (a small tracked tractor) with a mechanical auger. Fertiliser is also applied to enable rapid early growth and to reduce the need for extensive tending after planting. Instead of using lines, planting is carried out below canopy gaps immediately after logging, when overstorey cover is minimised and before weeds have developed. This approach is most suited to larger canopy gaps and skid trails where access is possible for the machinery being used, but is less suited to off-road sites. Success is being measured according to cost per established seedling, rather than cost per ha treated. In contrast to Sabah, these particular trials are still at an early stage. |
This capacity may be limited if remaining undisturbed forests are small or distant. Most commonly, however, the major problem for forest managers is how to shorten the time until some form of commercial harvesting can be carried out once more.
There are two basic types of silvicultural intervention. One involves simply protecting the vegetation from further disturbances, and managing the existing stands by selective thinning or perhaps pruning the trees already present. This is likely to be most suitable for small-scale community forestry operations.
The other approach is to enrich the existing forest with tree species that are more commercially attractive than those that are already there, or that are only present in low densities. This approach requires more sophisticated practices, and is likely to be restricted to larger-scale operations.
Various types of enrichment planting have been tried including planting trees in lines cut through the forest (with close or wide spacings between these planting lines), or gap plantings with trees planted in only large gaps, or with intermittent small and large gaps in the canopy.
The diversity of approaches being tested in Malaysia (see Box 6) suggests a range of approaches will be required across the region depending on the ecological circumstances present. There is no single prescription that will suit all situations.
The economic advantages of enrichment planting are still unclear, although some promising results are being obtained in experimental conditions.
