Short-rotation plantations are characterized by the establishment of hardwood species; planted at relatively dense spacings (2,000 to 10,000 trees/ha); closely tended like an agricultural crop with the control of weeds and pests and the management of nutrients; and harvested on a 2 to 12 year rotation.8 However, the minimum requirements for successful commercialization are economically and biologically rigorous. These minimum requirements include good land, fast-growing plant materials, technical expertise, and experience. The requirement for experience is not to be taken lightly, as it is critical to understanding and dealing with all of the challenges associated with establishing and maintaining short-rotation plantations.
Before discussing the technical and economic aspects of short-rotation wood plantations, this chapter presents three actual case studies -- the Philippines, Hawaii, and Brazil. The inclusion of these case studies not only provides background information on the technical requirments for short-rotation forestry, but also highlights the importance of experience. For each case study, issues related to plantation management including establishment, maintenance, protection, growth and yield, harvesting, and wood transport are discussed. Chapters that follow will refer back to these case studies as needed and present addtional experiences as relevant.
In 1979, the Philippine government, recognizing the increased demand for fuelwood generated by a growing population, and hoping to substitute wood for imported fuel in some industrial processes, initiated programs aimed at developing and managing plantations for wood-energy. The government efforts favored action-oriented programs over those demanding extensive preliminary research -- over 60,000 ha in energy crops were planted. Planners recognized that mistakes would occur, but believed that corrections could be made as programs evolved. Significant problems did emerge and the Philippine experience offers important insights into factors influencing the success of programs to support wood-energy plantation development.
Various government agencies at the federal level implemented programs encouraging the development of energy plantations. These included the National Electrification Administration (NEA), the Farm Systems Development Corporation (FSDC), the Ministry of Human Settlement (MHS), and the Bureau of Forest Development (BFD). Programs established ambitious goals and were well-funded. Provincial, municipal and village plantations were attempted as well, although few successful plantations developed under local government programs. Private corporations and individuals also established tree plantations for fuelwood in areas where markets were dependable.
Programs differed in target audiences (which ranged from small farmers to corporations), level of financial and technical support provided, and intended energy markets. For example, the NEA's Dendro Thermal Power Program used wood to generate electric power for rural power grids, the FSDC's program produced wood for conversion to charcoal, and the NEA's TANGLAW Program produced wood for a variety of purposes with the marketing strategy dependent upon the location of the plantation.
While BFD programs are the largest in terms of acreage, the Dendro Program has been more extensively documented. The Dendro Program anticipated the development of 60 to 70 wood-fired electric powerplants that would be supported by multiple energy crop plantations of 1,100 ha or more. Wood to supply the powerplants would be grown by upland farmers recruited by the NEA rural electric cooperatives that would manage the projects locally. Farmers were organized into associations of 10 families each. Support to farmers included: leases of government land at concessionary rates, loans to defray the costs of plantation establishment and management, technical assistance, infrastructure development, guaranteed markets, and health and medical benefits.
A report on the Dendro program covering the period 1980 to 1984 indicates that while planting success improved over time, tree survival and plantation cost effectiveness varied dramatically. Of 44 project sites, 13 had not yet established 100 ha of plantations, and five sites had survival rates below 10%. However, six sites had established more than 400 ha of plantation and nine sites had survival rates above 80%. Managers attributed this success to site suitability and secure land tenure. Managers suggested the following as contributors to failures: unfavorable soil conditions, free-roaming cattle, inadequate institutional support and poor organization, and the discontinuation of the farmer loan program. Plantations developed under private initiatives noted above were often more successful than government projects. Reasons reported include the establishment of plantations on better quality land and the provision of more protection to young plantations.
Site Selection. While procedures for plantation establishment vary throughout the Philippines with climatic, edaphic, social, and economic variations, commonalities may be discerned. The high population density of the Philippines means that there is a high demand for land in lowland areas with quality soils. Energy plantations and associated forestry production activities are usually relegated to roadless sites that are steep, rocky, and infertile. Surveys of NEA and FSDC energy plantation sites indicate that planting frequently occurs on 40 to 60 degree slopes, and soils with a pH below 5.0 predominate in some areas. The dry season at many project sites lasts 5 to 7 months. The lack of roads and trails at mountain sites complicates seedling distribution, silviculture activities, and marketing. Most of the land developed under NEA, FSDC and MHS programs was previously under BFD management. The BFD has been accused of refusing to relinquish the better lands under its control. In some areas, political forces have determined the location of plantations; these sites have generally produced poor results.
Species Selection. One species, the giant ipil-ipil (Leucaena leucocephala), represents more than 90% of the total area planted. While the tree grows rapidly, fixes nitrogen in the soil, is easy to manage, coppices readily after harvesting, produces excellent fuelwood and leaves that provide high protein livestock feed, it grows poorly at altitudes above 500 m or in soils with a pH below 5.5. Use of ipil-ipil in inappropriate settings has in some instances been disasterous. One Dendro Project site lost 1,021 of 1,031 ha planted. Efforts to diversify the species used are now underway.
Plantations are usually established on areas of grass or brush, although secondary forests are occasionally converted. Clearing, therefore, can usually be accomplished without chain saws or heavy equipment. Competing vegetation is removed by slashing with machetes followed by burning. Virtually all tree planting is done by hand. The recommended spacing is 1 m x 1 m (10,000 trees/ha). Although container grown seedlings have the highest survival rates, direct seeding is more common. With favorable soil and water conditions, direct seeding can be as successful as planting seedlings. In some cases, direct seeding results in overstocked stands because farmers tend to plant several seeds at each planting mound. Overstocked stands mean few stems grow to desired diameters. Little thinning occurs for various reasons. Some managers fear thinning would lead to overcutting, while some farmers feel that returns would not offset associated labor costs. In many places, upland crops are planted along with (or before) seedlings and harvested before the tree canopy closes. Cultivating crops tends to lead to more effective suppression of competing weeds and grasses and more active protection of trees from fire and livestock. Plowing is expensive and most slopes are too steep or rocky to permit its use.
Plantations require weeding frequently until the trees reach a height of 1.5 to 2.0 m or until the canopy begins to close. At least three weedings at two month intervals are necessary before trees overtake grasses. Grasses and weeds are typically cut by hand and placed at the base of young trees for mulch. Upon reaching 2 m in height, little maintenance is required. Plantations may be checked two to three times a week to guard against livestock, fires and illegal woodcutters. Fertilizer is not commonly applied because of its high cost. Serious psyllid infestations have been encountered in many leucaena plantations; however, farmers are reluctant to invest in insecticides to protect trees. While most trees survive, growth may be severely curtailed.
Growth rates of energy plantations vary greatly, depending on the quality of the site and plantation management. The NEA plantations experienced annual growth rates that range from less than 20 m3 (8 tonnes)/ha to 90m3 (36 tonnes)/ha.10 Annual growth averages 40 m3 to 60 m3 (16-24 tonnes)/ha. Under average conditions, trees used for charcoal or firewood are harvested after 3 years. Subsequent coppice crops may be harvested after 2 years. Plantations producing fuel for dendrothermal powerplants have been harvested at 3 to 5 years. At this point the trees have a diameter at breast height of 5 to 13 cm. Coppice crops reach harvestable size in 2 to 4 years.
Harvesting and transport are difficult and expensive. At harvest, most energy crop plantations are clear cut 15 to 25 cm above the ground. Small branches and tops are trimmed and left in the field. Harvesting is done with chain saws, machetes or both. In some cases, harvesting with chain saws has been abandoned in favor of machetes. Unfamiliarity, fuel costs, and maintenance problems are identified as reasons. A 1981 study by the International Labor Organization found that handtools were cost competitive with small chain saws. Harvesting production rates vary with equipment, topography, and the skill, strength, and stamina of operators and laborers. At the Panalco I site, individual laborers harvest 1.5 m3 (600 kg) on average each day using machetes. At Casureco IV, workers with chain saws fell about 30 m3 each day. Trees are trimmed and stacked by other workers. Daily wages for wood cutters reflect prevailing rates for unskilled labor. Chain saw operators are considered semiskilled and receive a wage premium. The pakayao method (pay for work performed) is applied at most sites.
Forwarding wood from the point of harvest to loading stations is a
significant challenge because of rugged topography and the lack of roads and
trails. Initial plans called for the use of motor driven skylines at a number
of plantations. Twenty winch systems were purchased at a per unit cost of
approximately $27,000. However, Durst found that the feeder winches system was
still in use at only one plantation. Experience at Casureco, the plantation
continuing the use of the winches, indicates that considerable time and skill
are required for setup, the winches are not easily transported to rugged
roadless areas, and fuel and maintenance costs are significant.
Significant problems were encountered in the Philippine wood-energy programs in the 1980's. Many plantations failed and overall the Philippine program would be judged to have been unsuccessful. For plantations that survive, yields and incomes are often less than expected. Factors contributing to the failure of these programs include actual yields that fell short of forecast yields, problems related to the difficulty and cost of forwarding and transport, irregularities in the administration of project funds, and, in some areas, problems related to peace and security. Additional problems are specifically related to the biomass powerplant projects. These include power plant design deficiencies (particularly related to fuel preparation and handling), and contracted wood suppliers who sold wood to other markets.
Durst suggests that additional research into problem areas is needed for future program viability.12 Such research would include: alternative native species; the economic effect of plantation stock density (maximized biomass vs. increased planting, tending and production costs); optimal tree size at harvest; alternate forwarding and transport mechanisms; effects of repeated biomass harvest on soil fertility; and opportunities for improved project analysis (by adjusting market prices for distortions due to taxes, subsidies, trade restrictions, etc.).
Today the Philippine Department of Environment and Natural Resources (DENR) is attempting to attract the private sector to plant trees on open and denuded government lands. Affordable long term leases are offered on substantial areas (up to 40,000 ha), on the condition that trees are planted on a specified area within a specified period of time.
Although groups in the Philippines have generally shown little interest for renewed efforts to produce electricity from biomass, one private sector group is currently working toward the development and operation of 10 MW electric powerplants fueled by biomass. Fuel supply is considered the most formidable hurdle. The plants would be fueled by wood chips and it is estimated that each 10 MW plant would require approximately 155,000 tonnes of green wood chips annually. About 14,000 ha of marginal land would be needed to sustainably supply this fuel volume. The proponent proposes a five year crop rotation program, and desires a long-term fuel supply agreement with a supplier holding at least 30,000 ha under a DENR reforestation program. Fuel delivery would be the responsibility of the supplier. The proponent indicates that the key criteria in fuel supplier selection would be a track record in establishing and operating a tree plantation of at least 15,000 ha, and the financial resources to guarantee fuel supply. Potential fuel suppliers include logging companies, and pulp and paper mills.
Hawaii's current dependence on petroleum as a source of energy, its distance from sources of fossil fuel, and its history of electric power generation from bagasse (residue from sugarcane processing) contribute to the appeal of energy crop production in Hawaii. In 1978, a joint research and development project to produce woody biomass for energy was initiated between BioEnergy Development Corporation and the U.S. Forest Service. The U.S. Department of Energy funded this effort for 10 years through its Short-Rotation Woody Crops Program. The project resulted in the establishment and management of 289 ha of eucalyptus tree farms.
Site Selection. The Hawaii Department of Lands and Natural Resources inventoried lands within the state for their potential to support forestry activities. Two categories, prime 1 and prime 2, are most suitable for intensive culture of Eucalyptus or other fast growing tree species. More than 243,000 ha are included in these categories. Of the 243,000 ha, approximately 93,000 ha now lie fallow or are in sugarcane, brush, range or pasture. Nearly all the remaining acreage is in forest. Although the bulk of lands suitable for growing short-rotation energy crops are located on the island of Hawaii, each major island has significant forest development potential.
Field trials were established in two areas on the island of Hawaii, along the east (Hamakua) coast and south coast (the Ka'u District) at elevations from 300 to 600 m. The Hamakua sites receive 5080 to 6220 mm of rain each year; the soils are highly weathered silty clay loams developed on volcanic ash. The Ka'u sites receive 1020 to 2290 mm of rain each year with four or more dry months; the area has rocky, organic soils that have low nutrient retention capacity. Total soil nitrogen concentrations vary widely, in both areas. At each of the two major locations, eight different sites were chosen to represent variations in elevation, soil characteristics, topographic and climatic conditions. Land used included recently harvested caneland, abandoned caneland, ranch lands, wasteland, and forest land. 14
Species Selection. Ten species trials were established between 1979 and 1984. Thirty species in total, including 15 eucalyptus species and twelve nitrogen-fixing species, were screened. As a result of the trials, Eucalyptus saligna and E. grandis were used most extensively in the plantings. Albizia falcataria, a nitrogen-fixer was chosen for use in mixed plantings. A. falcataria performed well on wetter areas, but its performance in the dry sites at Ka'u was judged unsatisfactory. Additionally, the dense foliage of the species contributed to breakage or blowdown in high winds, which was a factor at certain test planting locations. Test plantings indicate that poorly to somewhat poorly drained soils produce low biomass, as do locations with shallow soils or soils that have experienced substantial erosion. Researchers concluded that fertilizer application was unlikely to increase productivity in these settings.
Plantation Establishment, Tending and Protection. Planting stock is raised in small containers (or dibble tubes) at a nursery. The approach is labor intensive because the size of the operation did not justify investment in a automated system. About 450,000 seedlings can be produced annually; 150,000 in each of three four month cycles. The dibble tubes have a volume of 65 cm3, and are filled with a 2:1 mix of vermiculite and peat moss. After seeding, racks of tubes (100 tubes/rack) are stored in a roofed shadehouse and watered by an automated sprinkler several times a day. Germination occurs in 5 to 7 days; thinning to one plant per tube is done at 3 to 4 weeks. At 4 to 6 weeks (7.5 to 10 cm), seedlings are moved outside to harden off under full sunlight. At the nursery, rainfall is over 5000 mm/year and, therefore, it is not possible to harden (acclimatize) the seedlings by withholding water. Outplanting occurs 3.5 to 4.0 months after sowing when seedlings are 30 to 38 cm tall.
On abandoned caneland (which had been out of production for periods ranging from 3 months to 25 years) and wasteland, a low ground-pressure tractor equipped with wide gauge shoes is used to pull a heavy-duty off-set cutaway harrow. On very rocky soils, a heavy roller is used to crush vegetation. In areas with particularly heavy vegetation and brush (e.g., those that had been abandoned for many years), a tractor equipped with a bulldozer blade is used to knock down brush so that the harrow or roller can then be used. Vegetation on cleared land is allowed to regrow 6 to 8 weeks. Similarly, volunteer cane on recently harvested caneland, is allowed to regrow for 6 to 8 weeks. At this point, the area to be planted is sprayed with a contact herbicide/pre-emergent herbicide mixture by a tractor drawn spray rig. However, the pre-emergent herbicide is ineffective and not used if the soil is mostly covered by mulch.
Seedlings are transported to the site in enclosed trucks or trailers to avoid wind exposure. Because of the small scale of operation, planting is done manually. A two person crew is used; one worker opens holes with a metal dibble or spade-like bar and the second worker places the seedling in the hole and compacts the soil around the hole. About 600 seedlings can be planted per person-day at Hamakua sites. Planting in the rocky soils at Ka'u requires about twice as much time (300 seedlings per person-day).
Plantings generally receive two fertilizer applications and two herbicide applications within the first year. Fertilizer is applied at, or soon after, planting and also at six months following planting. A nitrogen, phosphorus, and potassium fertilizer (14-14-14) is used. Subsequently, only nitrogen is needed at most sites. Experiments with mixed plantings of Eucalyptus and Albizia falcataria, a nitrogen fixer, showed that at some sites it is possible to eliminate nitrogen applications beyond the first year by establishing appropriate admixtures of these two species.
The first herbicide treatment is provided 2 to 3 months after planting; the second application is performed only where needed at 5 to 6 months. Manual backpack sprayers are used. Additional herbicide applications may be needed with larger tree spacings as crown closure occurs later, however, the larger spacings also allow the use of mechanized mowing to control competing plants. Special care is required to avoid spraying the seedlings with herbicides because the young foliage is extremely susceptible to herbicide damage.
The spacing of trees in short-rotation plantations affects individual tree growth rates, stand productivity, plantation management cost, and harvest costs. Higher planting densities have higher wood production rates in early years, but, in addition to higher planting costs, an associated decrease in the growth rate of individual trees results in higher harvesting costs. Although stands planted at densities of 1.5 m2 and 3.0 m2/tree had the highest biomass production, the trees were small and, on average, did not attain the minimum acceptable diameter for cost effective harvesting (15 cm). Increasing growing space had little effect on tree height in the first two years, but resulted in substantially taller trees in later years. Tree diameter growth was even more strongly affected by increased spacing than was tree height. At an age of 6 years, trees planted with 12 m2 of growing space weighed 2.5 times as much as trees with 3 m2 of space. On a per hectare basis, however, the wider spacing produced only three-fourths as much biomass by age 6.
The accelerating growth of trees (age 5-6 years) that are planted at larger spacings is an important consideration in decisions on rotation length, especially if tree size is a significant factor in the cost of harvesting or in product value. In some cases, the productivity difference between spacing treatments begins to close rapidly in plantings of this age both in terms of total biomass and mean annual biomass. At the Chin Chuck test planting, for example, trees planted with 12 m2 of growing space are adding biomass at the rate 45 to 50 kg/tree annually, while trees at a 4 m2 spacing are growing at about 15 kg/tree.
Studies on the research plantings have defined the "operating" maximum diameter density line, the maximum number of trees (tree density) that can be grown to a given mean stand diameter without incurring levels of competition that result in a significant number of dead or unusable trees. Researchers concluded that to achieve a minimum acceptable mean stand d.b.h. (diameter breast height; approximately 1.4 m above the ground) of 15 cm at 5 years, the initial spacing should allow at least 6.7 m2 of space per tree.
Factors, other than growth patterns, affect plantation management and decisions on issues such as rotation length. Some of these factors, which include product requirements, nutritional effects, environmental impacts (e.g., soil loss), and economic factors, are discussed briefly below. Product requirements in the use of biomass as fuel do not place significant constraints on rotation length as the total biomass is usable. In the production of high quality pulp, however, leaves, bark, and limbs are removed. As bark and foliage increase as a percent of total biomass as rotation length decreases, the use of a crop as pulpwood would favor longer rotation periods. Shorter rotation cycles have the disadvantage of removing more nutrients from a site. Longer rotations effect nutrient drain in two ways: nutrients are removed from the site less frequently, and on a per unit biomass basis lower levels of nutrients are removed. This is the case because Eucalypts appear to have efficient internal nutrient cycling mechanisms, and, consequently, larger trees have lower average nutrient levels than do smaller trees.15 With regard to soil erosion, longer rotations in energy crop production reduce the potential for erosion because harvesting, which would be performed by clear cutting, is less frequent. However, compared to current agricultural practice in many areas suited for Eucalyptus culture, the potential for soil erosion with tree farms would be low. Sugar plantations on the Hamakua coast currently harvest to bare soil on a two year cycle, and soil loss can equal or exceed 2.5 to 5 cm/cycle.
Harvesting is the single largest cost item in short-rotation tree crops. In limited harvesting trials in Hawaii, felling, chipping and hauling represented more than 50% of total wood chip delivery costs. Harvest experience indicates that logistics and tree size are major determinants of harvesting costs. Harvesting systems that allow equipment to operate near full capacity will be important in covering equipment costs. The development of smaller, less expensive harvest equipment that is more suited to the requirements of harvesting small diameter trees would also help reduce costs. Studies indicate that during harvest, tracked equipment caused less damage to tree stumps and soils than did wheeled equipment. Conventional logging equipment that was designed for larger trees handled the research trees without difficulty, but the felling heads caused extensive damage to stumps and this contributed to unsatisfactory coppicing.
Based on information available to date, researchers in Hawaii believe that three short-rotation management regimes for Eucalyptus are particularly promising. The first regime consists of pure Eucalyptus stands under the shortest rotation (5 years) to yield a minimum acceptable tree size (15 cm d.b.h.). This is achieved with trees planted at a density of 6.5 m2 and regular fertilizer applications during the rotation cycle. Total biomass yield at harvest is estimated at 100 dry tonnes/ha (or 20 dry tonnes/ha/annual productivity). The second regime also consists of pure Eucalyptus stands, but tree spacing, rotation cycle, and final tree diameter breast high are greater (11 m2, 6 years, 20 cm d.b.h.). As with Regime No. 1, regular fertilizer applications are required during the rotation cycle. Total biomass yield is estimated at 112 dry tonnes/ha or 18.6 dry tonnes/ha/annually. The third regime is a mixed planting of Eucalyptus and Albizia. The Eucalypts and Albizia are planted in alternating rows 3 m apart. Within rows, Eucalypts are spaced 3 m apart; Albizia plants are spaced 2.1 m apart. In an eight year rotation without the application of fertilizer after the first year, this regime produced Eucalypts with a 23 cm d.b.h. and Albizia with a 11.4 cm d.b.h. Biomass yield, excluding Albizia, is estimated at 180 dry tonnes/per ha or 22.4 dry tonnes/ha/annually. Including Albizia, total biomass yield is estimated at 235 dry tonnes/ha or more than 29 dry tonnes/ha/each year.
The Hawaii case study is extensive with many significant results, which are
applicable to locations throughout the world. However, despite the results and
high growth attained, the competitiveness of plantation biomass for energy is
not favorable. The price of competing fuels, coal and oil, at present represent
significant challenges to the development of biomass for fuel on a larger
scale. Australian coal can be delivered to Hawaii at a price of just under
$60/tonne. Given the relative heat contents of biomass and coal, biomass needs
to be produced, harvested, and transported at costs under $40/dry tonne.
Another obstacle to the commercial production of plantation hardwoods has been
the inability of any group to obtain large tracks of land of 12,000 ha or more.
In late 1994 this obstacle was removed by the sale of the Hamakue Sugar Company
land to Bishop Estates and agreement with the state to gain access to an
adjacent 2000 ha. Bishop Estates anticipates establishing plantations on the
land but final use of the wood has not been determined.
Although Brazil represents half the land area of South America, its reserves of oil and coal are relatively small. Further, Brazilian coal is high in sulfur and ash and of relatively low quality. Brazil's search for alternative energy sources began with the passage of the Forest Code of 1965 and Public Law 5106 in 1966. These laws implemented incentive programs that affected the forest products sector and, as a result, the area of planted forest increased from 470,000 ha before incentives to 6.5 million ha in the 1993. A major fraction of the charcoal used in steel production and nearly all of the feedstocks used in the pulp and paper industry are now derived from these plantations. Eucalyptus plantations represent 51% of the planted forest area; the genus Pinus accounts for an additional 32% of plantings. A native species, bracatinga (Mimosa scabrella), is also used extensively in wood energy plantations in southern Brazil. The scale of short-rotation forest plantations in Brazil dwarfs the experience in other countries. Nonetheless, these plantations provide only 39% of the wood used for industrial purposes in Brazil.
Fiscal incentives were important factors in the development of a pulp and paper industry and a charcoal-based iron and steel industry in Brazil. The cement and composite board industries are also large consumers of plantation grown wood products. The growth of the pulp and paper industry, however, was probably the single most significant factor that promoted the development of large-scale eucalypt plantations in the 1970s. Brazil has become a net exporter of short-rotation based wood products including pulp and paper, plywood, hardboard, and pine lumber. Forest products production accounts for 5.6% of Brazil's Gross Domestic Product (GDP), 4% of Brazilian exports and approximately 2.5 million jobs in rural areas.
Another dimension of Brazil's experience with plantation forestry is the growing importance of farm forestry, including intercropping (agroforestry) of trees and food crops.18 Today farm forestry accounts for as much as 20% of the total plantation area, with some forestry companies expecting to raise this fraction to 50%. In the mid-1980s with the removal of federal tax incentives and objections by environmentalists to large-tract plantations, forestry companies began contracting with private farmers as a means to expand wood supplies. Typically, the forestry company provides the material (seedlings, fertilizers, herbicides) and technical know-how for establishing the trees on the farmer's land and contracts with the farmer to buy some or all of the first harvest for an agreed upon price that incorporates repayment for the initial inputs and services. Farmers are willing cooperators as the trees provide an additional source of income from a certain market, allow the productive use of marginal areas, stimulate cooperation with fellow farmers, and make available more wood for on-farm use. Forestry companies like farm forestry because capital requirements are lower (i.e., lower establishment costs), there are no direct tending or maintenance costs, and transport costs can be lowered because farms are usually within close proximity to mills.
Site Selection. When incentives were first introduced, no ecological zoning and no comprehensive body of scientific work existed to aid in choosing the best species for each region and site. Plantations were established in savanna-like regions in the central-west and southeast primarily because of low land prices. Climatic conditions in these areas, low annual rainfall and a 5-7 month dry season, were inappropriate for Eucalyptus grandis and E. salingna. These conditions, in concert with the remoteness of sites from potential product users, resulted in some major failures. In some cases, plantations never became well established because of limited groundwater availability or the presence of subsurface gravel layers that roots were unable to penetrate. Today much greater attention is given to site characteristics including existing vegetation, slope, chemical and physical characteristics of the soil, availability of water and energy, and distance from consumers.
Although native forest ecosystems have in the past been cut and burned to establish "reforestation" plantations, plantations are no longer established in areas with native forest cover. Further, rising land prices in industrialized regions over the last decade, and regulations by some states have made it difficult for forest companies to expand plantations in areas near their existing mills. Thus, companies have begun to emphasize higher productivity through genetic improvement of trees and careful soil management. Most plantations today are established on abandoned or degraded agricultural lands or on land previously occupied by eucalypt stands. Companies also prefer land that is flat or gently rolling to land with steeper slopes.
Species Selection. The most widespread Eucalyptus species in Brazil is E. grandis. Others include E. salinga, E. urophylla, E. camaldulensis, and E. citriodora. Hybrids, particularly urophylla X grandis, are showing very promising results in several parts of the country. The federal government, state governments, and forest product companies carry out active genetic improvement programs for these species. Controlled hybridization, cloning and micropropagation are used to achieve homogeneous stands that provide high productivity, natural resistance to pests and diseases, and uniform raw material. E. camaldulensis is the preferred agroforestry species because of its more vertical canopy, which leads to less shading of the food crop planted between tree rows. Beans are preferred crop to plant with the trees.
Bracatinga, a native nitrogen-fixing tree, is a key plantation species in the cold highlands of southern Brazil. Although bracatinga has lower yields than Eucalyptus, it is preferred by many farmers because it can be grown at a much lower cost than Eucalyptus, a large capital investment is not required, and there is no need for fertilization, tending and control of leaf-cutting ants. Stands are generally planted at a density approaching 20,000 seedlings/ha and later thinned to 3,000-4,000 seedlings/ha. On a seven-year rotation, Bracatinga yields about 13 m3/ha/annually. By the time a bracatinga plantation is harvested, seeds have been naturally incorporated into the soils and there is no need for replanting. Bracatinga has been collected locally by provenances and, like Eucalyptus, is the subject of genetic improvement trials.
Plantation Establishment, Tending and Protection. Vegetative propagation using stool beds or tissue culture is used to produce clonal seedlings. Seedlings are grown in dibble tubes filled with vermiculite or a vermiculite, compost, ground charcoal mixture. The nursery process for Eucalyptus seedlings requires 70 to 80 days. Seedlings spend the first half of the nursery period under shade; the second half in the sun. Most planting is done by hand. Seedlings are watered immediately after planting, and again after about a week, if rainfall has been limited.
Slash burning to prepare sites is rare today although it was common in earlier plantation establishment efforts. In early operations, harrowing, plowing and furrowing was conducted without regard to slope or runoff direction. The result was an enormous amount of erosion. Such intensive agriculture-like preparation is now being abandoned in favor of minimal cultivation techniques that reduce soil and nutrient loss. This approach involves the use of herbicides followed by furrowing that follows the contours of the site.
Plantings for short-rotation coppicing stands generally have spacings of 3 m x 3 m (1,100 plants/ha) or 3 m x 1.5 m (2200 plants/ha). Fiscal incentives initially favored denser plantations, but many early plantations, with densities of 5000 to 10,000 trees/ha, were failures because mortality was high, final diameter was small, and the percentage of bark to wood was too high. Brazilian experience indicates that the mean annual increment increases with wider spacings. Wider spacings also reduce wind damage, facilitate harvesting and weed control, and allow the intercropping of agricultural crops when desired. Today, spacing is adjusted to produce a tree of a specified diameter at harvest, given site quality, plant genetics and rotation period.
Because Eucalyptus is an efficient nutrient user, it ultimately contributes to nutrient depletion which must be corrected with fertilization. Short rotations cause more nutrient loss because nutrient uptake is higher in young Eucalyptus plants. Seedlings normally receive an initial fertilization of 120 g of NPK. Unlike early operations that applied a standard fertilizer formulation to sites indiscriminantly, companies today have specific formulations for each site, species, hybrid and clone.
In Eucalyptus plantations weed control is performed twice a year, and is considered critical until canopy closure occurs, usually after the first two years. Initially, Brazilian plantations used discing between rows, and hoeing within rows, to control weeds. Discing, however, contributed to erosion (since rows were usually oriented downslope) and also cut the surface roots of the trees, retarding growth and sometimes killing the tree. Today weeds are controlled by methods that do not disturb the ground surface, such as herbicides and mowing. Herbicides are applied just before planting and again at 4 to 8 months. Research has shown that sheep and cattle can also be used for the control of weeds, and that intercropping with agricultural crops can eliminate the need for tending operations during the first year.
Resistant clones, hybrids and species are used to control fungal diseases. The control of leaf-cutting ants is an expensive cultural treatment in Eucalyptus plantations. Leaf-cutters, once established, can destroy a young plantation in a few days. Consequently, plantations require careful monitoring to detect colonies at an early stage. The dodecachlor-based baits previously used to control ant populations were banned in 1992. A sulfluramid-based bait is now used.
Local insects, particularly the families Lepidoptera and Coleoptera, have caused problems for some eucalypts. Control was initially attempted via pesticides but environmental effects, growing insect resistance to pesticides and cost limited the effectiveness of this approach. The problem was partially alleviated through selection of species appropriate to sites and silvicultural practices such as pruning, but a major breakthrough occurred when the potential of biological controls was recognized. This is now the principle method of control used for insect problems. For example, many insects are controlled by encouraging the maintenance of local bird populations (by intermixing native vegetation with the eucalypts).
Eucalyptus harvesting is becoming increasingly mechanized. The felling of trees is usually done manually with chain saws. An average operator cuts 120 trees/day. Crowns are lopped off; trees may be cut into sections or left whole depending on the equipment used to move trees to the landing. Loading is done with grapple loaders. Nearly 70% of transport to mills is done by truck; the remainder occurs by rail. The haul distance averages 70 km one way, with maximum hauls in the range of 200-300 km. Transport fuel expense is a major concern to forest companies.
Bracatinga culture is an activity of smaller farms. Harvesting is generally done by axe. Logs are cut into 0.8 to 1.2 m lengths with a minimum 4 cm diameter. Horse carriers or tractor trucks transport logs to the roadside. Logs typically are sold from the roadside.
Productivity of short-rotation, large-scale Eucalyptus plantations in Brazil has increased dramatically over the past 2 decades. In some areas, annual yields rose from 35 m3/ha (16.5 dry tonnes/ha) in 1970 to 70 m3/ha (33 dry tonnes/ha) in 1993. 19 The increased productivity is the product of a substantial research effort, particularly in genetics and biotechnology, reinforced by better silviculture and management practices. Yields from farm forestry are somewhat lower, but establishment costs are lower as well.
Costs for one hectare of Eucalyptus on a seven-year rotation vary widely depending on the region, soil fertility, species, and technology. Logging and transport costs, for example, vary with region and terrain from 51% to 70% of total delivered wood costs. 20 The planting and cultural costs of bracatinga are low and, consequently, logging and transport costs may reach 93% of total operational costs.21 Because most farm forests were planted only recently (late 1980s), harvesting is just beginning. Indications are, however, that delivered costs will be about the same as those from forest company operations.
After harvest, logging slash is burned or used for energy purposes. If coppicing is used for regeneration, the area may be disced and the site is broadcast fertilized. Stump sprouts normally appear within 2 to 3 weeks. If the stand is to be replanted, stumps are removed or are covered with soil, and seedlings are planted in the rows between stumps. In the 1970s and 1980s, declines were observed in the yield of Eucalyptus stands established by coppicing. Factors that contributed to the declines included the establishment of plantations on inappropriate sites, inappropriate provenances, large genetic variation in the seeds used, the incidence of canker, leaf cutter ant attacks on sprouts, and the damaging of stumps by harvesting. Most problems with coppicing have been solved and coppicing systems may be applied with reasonable success. Lower costs of coppicing (about 10% of planting costs) offset, at least in part, the reductions in coppice yields (reductions of approximately 15% for the first coppice and 30% for the second). Brazilian companies, however, are moving to the practice of renewing stands after the first harvest because the rapid improvement of genetic stock makes replanting a more cost-effective option.
Brazil's experience indicates that successful plantation establishment efforts have direct links to an existing or planned end user. Further, successful reforestation efforts require a fully funded government oversight organization and existing educational and research institutions.
Environmental groups in Brazil now exert considerable pressure to limit
further eucalypt plantation establishment. Federal, state and municipal forest
legislation is becoming more restrictive. Critics of monocultural
Eucalyptus plantations claim that these plantings reduce biodiversity,
encourage soil erosion, reduce soil nutrients, lower local water table levels
and compete with the production of food crops. Reis proposed the following
actions to minimize the environmental impact of Eucalyptus plantations:
The forest companies have responded by emphasizing forest management that is increasingly directed at the sustainable use of forest resources that include water, air quality, erosion control, wildlife, recreational and scenic values in addition to wood products. Many of the large forest product companies now have environmental departments to address environmental concerns. The efforts of these companies include tree farmer programs in which small farmers are included in the forest company's supply planning and operations. These programs are expanding and will become more important supply sources in the future. Companies are also conducting research on agroforestry to provide the biological, technical and economic information needed to support such programs. Agroforestry programs, support of local education programs and donations made for the preservation of endangered ecosystems have enhanced the public image of forest product companies. These small farmer programs are also seen as a means to promote rural economic development, reduce migration to urban areas, and limit the growth in concentration of land ownership by forest companies.
There has always been intense public scrutiny of bracatinga use. Harvesting is permitted only for mature stands and only on a sustained yield basis. Widespread clearcutting of bracatinga is not allowed to reduce soil erosion and preserve water tables. The policy has contributed to a stabilization of fuelwood supply during a period of rising demand and, consequently to a rise in the real price of bracatinga. This has increased the income of thousands of small farmers.
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