Topic 7.6: Harvest Plans

With good maps in hand, felling areas, stream buffer zones, and other restricted areas (e.g., steep slopes) can be demarcated.  Likewise cost-effective road and main skid trail networks can only be laid out after good maps are prepared.  Maps of trees to be harvested and of future crop trees are of great value in laying out skid trails and log landings.  Standards for extraction route construction and maintenance, stream crossings, waste disposal, and etc. are available in most countries, but the FAO Model Code of Forest Harvesting (Dykstra and Heinrich 1996) is nevertheless worth consulting.

During harvest planning as well as during silvicultural operations themselves, careful attention must be paid to national, regional, or local environmental guidelines.  In most places there are restrictions on which species can be harvested and on the minimum diameters of harvestable trees.  Ways of making timber harvesting compatible with management of non-timber forest products, maintenance of wildlife populations, and protection of biodiversity should be specified.  For example, nest and den trees, fruit trees that are especially important to wildlife (e.g., figs), and stands near cave openings deserve protection.  Retention of extremely large trees is also generally recommended; these trees contribute a great deal to maintaining forest structure, can be good seed sources, provide important roosts and perches for wildlife, do an incredible amount of damage to the residual forest when they are felled, and often yield little usable timber due to stem rots, hollows, and other defects.

Before harvesting commences, field crews should be well trained in safe and environmentally-sound logging practices.  Sawyers should know how to direct the fall of trees using various cutting techniques (e.g., retention of holding wood) and with the use of felling devices such as hydraulic felling jacks and winches.  According to the International Labor Organization, logging is among the most dangerous professions in the world; safety training and appropriate safety gear (e.g., felling chaps, steel-toed boots, eye and head protection) are essential.  An overall objective should be to professionalize the forestry work force.  If sawyers and skidder drivers take pride in their work, they are more likely to strive to comply with environmental guidelines.  Paying workers solely on the basis of the volume of timber felled or yarded does little to encourage good harvesting practices such as directional felling and protecting soils and future crop trees from skidder damage.

Table 7.6.1.  Environmental, social, and financial conditions favorable and unfavorable for natural forest management.

Table 7.6.2.  Estimated road planning, construction, and maintenance costs for a lowland tropical forest on undulating terrain.  Best estimates given for moderate (0-5^o) and steep (5-12^o) slopes.

¹ Standard road with 5 m-wide clearing, 3 m wide domed working surface, with 25 cm of compacted gravel (available at a mean distance of 5 km), and side drains, constructed with a D-8 Caterpillar tractor.

² Bridge over a 5 m wide stream, log abutments and beams, soil and gravel surface constructed with a D-8 Caterpillar bulldozer and a backhoe.

³ Maintenance includes weekly passes with a motor grader during harvesting, re-gravelling at 6 month intervals, and cross drain opening with a D-6 tractor.

⁴ Hauling of 12-18 m3 loads with a truck without central tire inflation.  Includes fuel, lubricants, maintenance, and labor costs.

⁵ Includes opening of larger cross drains and installation of water bars with a D-7 and a backhoe.

Table 7.6.3.  Some timber harvesting regime options for natural forest management.  Only conditions related to regeneration and growth of the harvested species are considered; other potentially important environmental factors are not included.  For many non-timber forest products, there are analogous gradients in harvesting intensity.