The following discussion applies primarily to planted forests that will exceed a few hectares in size. Small-scale (1-2 hectare) woodlots can also be important components of the wood supply, but inputs such as seedlings, fertilizer, technical advice, as well as commitment to purchase the timber at harvest are often, in these cases, provided by private timber companies (Cellier, 1999). Even in these situations, however, some of the following discourse may empower the woodlot owner to establish more equitable agreement terms with the timber companies.
Two Approaches for Planted Forests
Two distinctly divergent approaches to planted forests are developing, and each has parallels in agriculture. Both are outlined here, and the choice of which path to follow will depend on the particular circumstances facing a manager.
Intensive Management Model. While hunter-gatherer societies once used more than 200 local species of plants and animals for food annually, the entire global population today relies for 70 percent of its food intake on only nine plant species, one bird and a few mammals. Sutton (1999) and others predict that planted forests will follow the same path and “we may eventually get most of our wood from four or five species”. This small handful of species will need to be highly responsive to genetic manipulation and stand management. A clear parallel in agriculture is the intensive domestication and genetic manipulation of cereal grain crops – and the accompanying global cultural adaptation to these grains. By the use of genetic engineering techniques, the usually long period required for introducing trait changes into trees may be shortened considerably (Tournier et al., 2003; Walter et al., 1998). Attempting to predict which tree species will become the final four or five candidates is futile, but, based on current interest and research, genera likely to be considered are Pinus, Eucalyptus, Populus, Acacia and some in the Verbenaceae (Raymond et al., 2004; Seling et al., 2001; Sutton, 1999; Turnbull, 1999; Wingfield & Robison, 2004; Pandey & Brown, 2000).
This intensive management scenario is most attractive to large industrial forestry enterprises (with parallels in agri-business). Although a disputed topic (Powers, 1999), some argue that intensively managed plantations can be healthier than indigenous forests, and have the potential for long-term sustainability (Gadgil and Bain, 1999; Evans, 2005). The establishment of predictable market conditions would, theoretically, provide long-term supply and demand parity, but may also introduce new challenges for pulp mill managers (Clarke, 2001). Intensive genetic engineering programs should increase productivity, and possibly properties (Lindstrom et al., 2004), over time, as well as theoretically providing the mechanism for controlling insect and disease problems. On the negative side, market maturity, wood productivity increases and improved insect and disease resistance are only future possibilities and they, along with fertilizer and labour inputs, will require large capital investment. The ability to control insect and disease pathogens through genetic engineering is quite speculative at this juncture, especially considering the speed at which pathogens can mutate compared to the time required to introduce genetic resistance into trees (Wikler et al., 2003). In the short term, at least, traditional pest and disease controls will be needed.
Diversified Market Model. Again referring to the agriculture model, although roughly 70% of our plant derived food may come from a very small number of species, the other 30% comes from quite a large number of species and varieties, particularly fruits (including nuts) and vegetables. Although we might survive on the nine plant species comprising the 70%, few would be willing to do so. Furthermore, as underdeveloped segments of society become more affluent, they will likely want a more diversified diet than they have traditionally relied on. This suggests that even if the intensive management model for planted forests becomes a reality, it will not serve all aspects of current market demand, and future market demand may become even more sophisticated. All of this points to a need for planted forests that will meet the needs of a diversified market, particularly as natural forests reach their limits for providing specialty woods.
For example, in New Zealand, as natural forest sources of totara (Podocarpus totara), a durable construction timber, and kauri (Agathis australis), a valuable boatbuilding wood, have dwindled, planted forests of Cupressus macrocarpa have been filling the market gap. Recently, other conifers (Cupressus lusitanica, C. macrocarpa, and the Chamaecyparis nootkatensis x C. macrocarpa hybrid) are being tested in demonstration plots as further alternative wood sources for these niche markets (Low et al., 2005). Kauri, itself is now being tested as a planted forest species (Steward and McKinley, 2005). These plantings may be on a smaller scale, utilize a larger number of species, have uneven age structure and have longer rotation ages (Mayhew and Newton, 1998), but will also likely have smaller capital investment requirements and yield higher market prices. Integrated pest control measures and careful matching of soil and climate to tree species will be needed. Market stability over the rotation age could be unpredictable, although for well-known species (teak, rosewood and mahogany) the risk is smaller. Because of longer rotation ages, shorter-term product recovery strategies may need to be incorporated into planning.
A good example is found in India where East Indian rosewood (Dalbergia latifolia) is planted as an overstory tree in tea plantations. Tea harvest provides a steady annual income while harvesting of rosewood trees when the crowns provide too much shade, yields occasional very high profits that can be re-invested in new plantations of rosewood and other valuable tree species. Similar opportunities exist with coffee plantations, particularly now that shade-grown coffee brings such a premium price in the market.
In the near-term, some amalgamation of the two models may be a viable solution, but since forestry requires very long-term planning, a manager should decide which of the two models best fits his circumstances and plan accordingly.
Regardless of the planted forest model of choice or the tree species chosen, five key pre-establishment assessments need to be made before beginning: (1) a social and environmental impact assessment, (2) a legal assessment, (3) a complete site analysis, (4) a market analysis and (5) a tree species adoption assessment. The following provides a brief summary of what is minimally needed in each of these processes, but should not be considered as inclusive. Particular situations will likely require additional research investigation. Additional sources of information on these subjects can be found in the Planted Forest Code (http://www.fao.org/forestry/plantedforestcode).
Social and Environmental Impact Assessment
An initial baseline assessment is needed, followed by long-term monitoring through planted forest rotation cycles. Potential environmental perturbations as well as considerations for the rights of indigenous peoples and cultures should be incorporated. 3
What will be the land tenure situation: Is the land to be purchased or leased or be part of a concession? Do indigenous peoples have traditional land-use rights that need to be addressed? What are the government policies toward planted forests? Are carbon credits a possibility? Does the country have a forestry bureau or agency, and if so what are its laws or regulations? Does the forestry bureau operate more or less independently, or is it subject to political influence? Do export bans apply to certain wood species, and do they apply equally to planted and natural forests? Do government officials recognize forest certification, and if so, by which certifying agencies? How stable is the government and its infrastructure?
Temperature range and extremes, annual and monthly rainfall (particularly as it relates to seasonality), access to water if needed for irrigation, soil depth, soil fertility, soil chemistry and pH, presence of soil insects or pathogens, topography, aspect, location and distance to primary processing facilities, transportation network and road conditions at various times of the year, available workforce and salary expectations of workers should all be part of an initial assessment prior to planted forest establishment (Wingfield and Robison, 2004; Raymond and Muneri, 2000; Pandey and Brown, 2000; Powers, 1999). Special considerations will be needed for certain species. For example, many planted Eucalypt species have the reputation of ‘water pumps’ because they have no stomatal control of leaf transpiration and, therefore, can quickly draw down local water tables (Calder et al., 1992). Species for which special heartwood characteristics, such as bio-deterioration resistance, are important need to be carefully matched to soil chemistry and pH, as previously noted. Even minor chemical elements in the soil may be quite important. Boron deficiency can lead to thinner cell walls in Pinus radiata (35% thinner in earlywood and 25% thinner in latewood), and may also affect lignification of walls (Skinner et al., 2003). These differences can significantly affect strength properties.
Short-term prospects, long-term expectations, finding specialty niche markets, local vs. export markets, primary processing (portable bandsaws, borate treating tanks) to increase value and to open export market potential, creating markets for crooks, limbs, roots, coppice and non-wood products, all need to be considered during initial planning. If the plantation will be a jointly owned by shareholders, then balancing their needs for short-term return against long-term economic sustainability will need to be part of the planning.
Tree Species Adoption Assessment
In choosing a tree species to plant, precise botanical identification is essential. Trade or common names are often meaningless, vary from place to place and may apply to several species. In some cases companies have established registered trademark names that obscure the true botanical identification. Only documented material with botanical (Latin) designation and source should be accepted. Where different genetic varieties or provenances are available, these need to be precisely identified and documented. Clearly, the choice of species needs to be well integrated with site and market assessments.
Tropical to semi-tropical planted forests can be established for a variety of reasons, but if the major goal is wood production most will fit into one of five general categories: (1) softwood plantations for paper or reconstituted wood products; (2) hardwood plantations for paper or reconstituted wood products; (3) softwood planted forest for solid wood or veneer market; (4) hardwood planted forest for solid wood or veneer market; (5) mixed species planted forest producing for various markets. Each of these is critiqued with a set of wood property issues and planting issues that are most critical to the type. Properties previously discussed at length are only highlighted here - for more details return to the appropriate preceding sections.
Smaller-diameter, shorter rotation stems than are needed for solid wood markets are often acceptable for chip-based products. Desirable properties for paper and panel products are often similar but differ sufficiently that they are discussed separately here.
WOOD PROPERTY ISSUES
• Paper and Paper Products
Higher density wood is desirable for increasing pulp yield and improving tear strength, resistance to beating and improving bulk. Best for Kraft paper. Lower density, often juvenile wood produces lower tear resistance and lower yield, but provides paper with high tensile strength and good folding properties. Best for writing and tissue paper; poor for newsprint. Avoidance of compression wood is important because it increases difficulties in pulping, reduces yield and is wasteful of chemicals. Knots, decay and bark contaminants reduce yield, are wasteful of chemicals and if not removed can produce unacceptable paper - even low-value tissue.
• Wood-Based Panel Stock
For most chip and particle-board products a relatively low density is preferred – generally between 0.25 and 0.45 g/cm3 (Zhang and Gringas, 1998). Higher density woods are difficult to compress and produce panels of excessive weight. Gradual-transition softwoods provide more uniform chips, but abrupt-transition species that are growing rapidly in moist-tropical regions may produce similar, low-density, uniform chips – Pinus radiata, for example. The presence of compression wood dulls knives, lowers yield and can introduce weak pockets due to poor adhesion with resin. A low threshold of knots, decay and bark contaminants is often permitted, but excessive knots can quickly dull knives and produce unacceptable product.
PLANTATION MANAGEMENT ISSUES
• Since juvenile wood with low density is acceptable for many paper and reconstituted wood panel products, trees can be planted with wide spacing and fertilized and irrigated if necessary, but early pruning is necessary for capturing most markets and gaining highest return. Tree spacing needs to be uniform to avoid unbalanced crowns that will increase the percentage of compression wood. Because the trees will be widely spaced, very windy sites, especially those with a prevailing wind from one direction should not be chosen as this will lead to excessive amounts of compression wood. If species are planted as exotics or in climates different from indigenous sites, wood property changes need to be anticipated and assessed for acceptability. In general, abrupt transition conifers will have lower density and less prominent latewood when moved from warm-temperate to moist-tropical conditions. Choosing improved provenances, if available, may be cost effective in some cases. Insect and disease management will be critical in these monoculture plantations.
As is the case for softwoods, small diameter stems are generally acceptable. Paper is the primary market except for low density species like Populus or Gmelina that also can be used for panel stock.
WOOD PROPERTY ISSUES
• Paper and Paper Products
Fiber length is shorter in hardwoods than softwoods, and when combined with thicker walls can yield paper with lower tear strength. Higher density hardwood pulp is generally ideal for kraft paper especially if mixed with fiber from a higher density conifer, such as Pinus caribaea (McNabb and Wadouski, 1999). The low density, juvenile wood of very short rotation Eucalypts and Gmelina spp. yield fiber best suited for tissue, writing and printing paper (Campinhos, 1999). Harvesting Eucalypts, before the age of 6 or 8 years also avoids wood that has high polyphenolic extractive content which greatly increases the difficulty in chemical pulping (Zobel, 1984).
• Wood-Based Panel Stock
Low density species, such as Populus spp. and Gmelina spp.,, can be chipped for board stock (Heilman, 1999). Higher density species can provide furnish for laminated veneer lumber (LVL) or finger-jointed lumber, but larger diameter stems are generally required than for paper.
PLANTATION MANAGEMENT ISSUES
• Basically the same issues exist for hardwoods as were noted for softwoods, except that juvenile wood is much less a concern and tension wood is the form of reaction wood in these trees. Internal stresses could become a problem if trees are grown to larger diameters.
Although some new, thin-kerf, bandsaw mills can handle small diameter logs, the yield is so low this is generally impractical. Both the lumber and veneer markets will require larger diameter logs. Most softwood lumber and ply markets are focused on construction materials; hence strength properties rather than aesthetics dominate. However, smaller niche markets, such as furniture, boatbuilding and musical instruments may require some combination of mechanical properties, resistance to bio-deterioration and aesthetics.
WOOD PROPERTY ISSUES
• Increasing stem straightness and decreasing taper are key ingredients to improving lumber or veneer yield; and for many products knots need to be limited. Wood density will be a primary concern as a direct monitor of bending strength and stiffness. The proportion of juvenile wood and compression wood need to be limited. In cases where significant proportions of juvenile wood are permitted timber design standards will need to be adjusted to avoid compromising current standards (Anonymous, 2006; Kretschmann, 1997).
PLANTED FOREST MANAGEMENT ISSUES
• Trees destined for lumber or veneer markets will require closer spacing at planting, with one or more pre-commercial or commercial thinnings. Pruning will ensure the highest value markets. Planting trees outside their natural climate ranges or seasonality limits may lead to timber production that fails to meet minimum acceptable wood density and strength standards (Turner et al., 2001; Zobel, 1984). Abrupt-transition conifers will require the greatest scrutiny. The use of genetic varieties may overcome some of these problems, but provenance trials will be needed before committing to large-scale planting. For specialized markets where bio-deterioration resistance is important, soil analyses may be critical. Disease and insect pest control will be critical factors in the success or failure of these longer-rotation monocultures.
Unlike the situation for softwoods, aesthetic considerations are often key factors in many hardwood markets (furniture, flooring, panelling). But mechanical and physical properties such as strength (furniture), hardness (flooring), dimensional stability (boat decking, garden furniture) or sound transmission (musical instruments) also may be very important to consider. The range of hardwood market niches is broader than for softwoods, generally requiring more specialized attention in species choice, matching to site and management practices.
WOOD PROPERTY ISSUES
• For solid wood and surface veneers of plywood, properties that closely match those found in wood from natural forests is generally the goal. Interior plies of furniture or panelling grade plywood are often produced from a low density hardwood that is easy to peel, with surface plies of a decorative wood. Exterior and marine grades have the highest quality requirements (knots and voids) and are generally made from a single species. Biodeterioration resistance may be a requirement for some markets. A minimum log diameter is generally required for veneer, and juvenile wood is to be avoided.
PLANTED FOREST MANAGEMENT ISSUES
• Many of the same issues listed for softwoods apply here, although the market niches are so diverse that management strategies need to be closely linked to market expectations. Soil pH and chemistry may be critical for producing expected heartwood colour and decay resistance. Since longer rotations will be needed for many markets, a mix of species with differing harvesting ages may be desirable. Agro-forestry, particularly using valuable hardwoods as shade for tea and coffee plantations, can provide steady income during a long rotation age. Uneven age management can also provide benefits for shade tolerant species or for controlling shoot borers or other insect pests.
This category comes closest to natural forest management, except the species mix is more controlled by not relying on natural regeneration. Species such as mahogany are particularly adapted to this sort of strategy, especially when combined with faster growing species to bring early financial returns. Shoot borer attack of mahogany in a mixed, multi-story canopy, planted forest is minimized as well. Wood property and forest management issues are basically the same as noted in the previous sections, but even more attention to specialty markets may be possible (crook timber for boatbuilders, musical instrument woods, etc.).
3 See the FAO Code of Conduct for Planted Forests for explicit details.