3.0. SELECTED CASE EXAMPLES

3.1. General gains from choice of species and provenance

The practical importance of systematic exploration and testing has been convincingly demonstrated through a number of internationally coordinated species and provenance trials. Among the earliest of these were range-wide trials started in the mid 1960s using provenance seedlots of Eucalyptus camaldulensis, an Australian species which for decades had been widely planted as an exotic, for the provision of fuel, shelter, posts and poles. The results from the trials, coordinated by FAO, which were established on 32 sites in 18 countries worldwide, showed that the potential gains in growth and yield which could be achieved simply by selection of the best-adapted provenances for prevailing environmental conditions, amounted to several hundred percent. The difference in yield between the best and the worst provenance within this same species was in these trials, 300% in northern Nigeria and 800% in Israel. These results were reported when the trees had gone through approximately one-third of the rotation age, and this trend has continued also later (Lacaze 1977, Palmberg 1981). The biggest differences in performance were between those provenances coming from summer and winter-rainfall areas, respectively: the use of provenances adapted to winter-rainfall (Mediterranean-type climate) regimes in summer rainfall (tropical) areas lead to poor results or at times to out-right failure. This general observation can be made also in a number of other species: provenances which are adapted to markedly winter-rainfall areas are no option in summer rainfall areas.

Highly encouraging and rather spectacular results are forthcoming also from evaluation of dry-zone Acacia and Prosopis species and provenance in an on-going, inter-regional program coordinted by FAO in technical collaboration with the DANIDA Forest Seed Centre, Denmark (Palmberg 1986, Graudal and Thomsen 1992); and from provenance trials involving humid tropical Acacia species, such as Acacia auriculiformis A. crassicarpa and A. mangium (see e.g. Puangchit et al. 1996, Nguyen Hoang Nghia and Le Dinh Kha 1996).

3.2. New Zealand

During the first 50 years of extensive European colonization of New Zealand, from about 1850 through 1900, wood for both domestic use and a substantial export trade came abundantly from the indigenous forests. But it was then realized that the indigenous forests could not sustain continued wood export, and would not even be able to satisfy continued domestic needs. After about 20 years of investigation and planning, both government and private organizations set out to replace the supply of wood from indigenous forests with wood from forest plantations. Thus began the world-famous New Zealand school of plantation forestry. By the 1950s, the goal of assuring a domestic wood supply had been achieved, and additional lands were being planted to re-establish an export industry. By then, the most common species planted were Pinus radiata and Pseudotsuga menziesii, both from western North America.

Pinus radiata was introduced into New Zealand in the mid 1860s. Selection and breeding based on local “land race” material, of largely unknown origin, was started more than 35 years ago without awaiting provenance trial results,. Research, including studies on monoterpene composition, indicated that the New Zealand “land race” consisted of a mixture of from one-half to two-thirds of the provenances of Año Nuevo and Monterrey (USA). In subsequent provenance trials covering the full natural range of the species in USA and Mexico and established on a range of potential planting sites in New Zealand, marked provenance differences were evident. For stem basal area per hectare, at the one site, Monterey outperformed Año Nuevo and the New Zealand material by 76% and 33% respectively. However, the pattern of differences between provenances varied widely among sites. A single provenance trial would thus only provide a snapshot of the comparative performances of the various provenances of Pinus radiata (Burdon et al. 1998). In some cases, the provision of one type of information, e.g. on resistance to climatic damage or disease resistance, virtually obliterated other types of information, such as growth potential and inherent tree form. The importance of establishing a range of provenance trials, on sites representative of the potential planting sites, was thus very evident (op.cit).

Experience and research in New Zealand challenged concepts underlying the traditional European-style forest plantations, and more-aggressive and more-intensive forest plantation management was increasingly instituted. New Zealand’s indigenous forests were growing 2 to 4 m3/ha/year but, by the 1980s, the forest plantations were commonly growing between 20 and 30 m³/ha/year. Thus it became clear that, for every hectare of forest plantation harvested, nearly 10 hectares of indigenous forest could be, in principle, set aside for uses other than wood production. This was largely institutionalized during the past two decades, and 23% of New Zealand’s land area is now in indigenous forest parks and reserves. More than twice the wood needed domestically is produced in exotic forest plantations which occupy only about 6% of the land area. Most of New Zealand’s environmental community solidly supports the forest plantation program. This is because it is clear that, without the forest plantations, the indigenous forests would by now have been much changed or even wholly cutover, to the detriment of many elements of the indigenous New Zealand biota. It should be noted, importantly, that New Zealand was able to achieve this turn-around, in part, by carefully keeping a stable human-population size.

3.3. Australia

Australia has followed a similar but somewhat different course. Its eucalypts, acacias and other indigenous angiosperm species were among the fastest-growing on Earth but, like other Southern Hemisphere conifers, most of its indigenous conifers were slow-growing. Recognizing that, Australia began forest plantations with Northern-Hemisphere conifers a few years earlier than New Zealand, but was slower to commit to them. Most Australian conifer-plantation sites proved to be substantially less productive than those in New Zealand. However, work done by CSIRO in the past few decades has shown how inputs of fertilizer, water, and other factors discussed above, can bring those forest plantations up into the 20+ m³/ha/year range. Some of the Australian work on site-preparation has been particularly instructive. A worrisome drop off in productivity after the first rotation on some sites has been associated in part with the invasion of competing exotic weeds in later-rotation forest plantations, and in part with the use of fire in their site-preparation. The weeds can be fought, and fire can be replaced. By mechanically shattering logging-slash on site and working it into the top 15 cm or so of soil, nutrients that would have been volatilized by the fire or quickly flushed from the ash by rainfall, stay on site and slowly become available to the new trees over many years as the shattered organic material decays. These lessons learned in Australia would seem to have broad application throughout the world.

3.4. China

Australian tree species have been planted in China for more than 100 years, but before the 1990s, there had been little efforts to determine which species and provenances were best for the local climate and soils and for the required end uses.

Eucalypts were introduced into southern China about 1890, and now cover an estimated area of 1.5 million hectares. When expansion of the Eucalyptus area began, the trees were raised from local seed sown in traditional nurseries, and planted on infertile sites without fertilizer. Only the most robust species (Eucalyptus exserta, E. citriodora) survived. These species tolerate infertile soils, but have low yields and wood with relatively poor pulping qualities. The average yield of forest plantation grown Eucalyptus in China has been only 5-8 m^3/ha/year.

In southern China, Acacia confusa has been widely used in plantings around houses and along roads, railways and waterways. It is relatively slow growing and has a crooked stem so that its principle use is fuelwood and shelter. The source of the original seed introduction was unknown.

In 1980 an Australian forestry mission to China recommended testing new introductions of species and provenances of the two genera mentioned above to increase forest plantation productivity. It has been demonstrated subsequently that substantial increases in yield could be obtained through the introduction of new species and strategic application of fertilizer.

Early results from trials showed that Eucalyptus citriodora and E. exserta could, with advantage, be replaced with E. urophylla in tropical areas with low typhoon risk, E. tereticornis or E. camaldulensis in tropical areas with high typhoon risk, and E. grandis and E. urophylla in sub-tropical areas.

Table 1. Yield and Cost Reductions.

Source: McKenney, 1998.

In regard to Acacia species, it was recommended, based on trials, that Acacia auriculiformis be used in the tropical lowlands, especially for boundary plantings; and the faster-growing A. crassicarpa and A. mangium be used on the slopes of the hilly land in tropical areas.

Non-market benefits included an estimated 80% gain in essential oils harvested from Eucalyptus plantations. The forest plantations of Acacia spp. fix atmospheric nitrogen and the new introductions produced tannins in larger quantities than the species previously used. Up to 230 kg/ha/year of nitrogen is being added to the soil in the Acacia plantations through natural N-fixation, which will reduce the need to use fertilizers. Up to 750 kg/ha/year of tannins are expected from some forest plantations. Using a discount rate of 5%, base-case benefits to China have been estimated at a net present value of $A122.3 million (1996). Internal rate of return is 35% (McKenney, 1998).

The research and development on tree improvement in China has potential applications and benefits also for other countries of the region.

3.5. Europe

Europeans had few indigenous food species amenable to domestication. Rather, their geography permitted early contact and trade with the Fertile Crescent and the Far East. They began receiving domesticates, and organizing concepts such as written language, from those regions over 5 000 years ago.

Much more recently, but (with the exception of China and Japan) otherwise early by world standards, Europeans began extensive plantation forestry. Although species such as Pinus pinaster were planted regionally with good success, the main focus was on two widespread indigenous conifers, Pinus sylvestris and Picea abies. Neither of these has proved to be a very good candidate for domestication, although the spruce is perhaps more promising than the pine. As with most temperate and boreal members of the Pinaceae, both are sensitive to changes in photoperiod, which cues various physiological functions for them. Their transfer to colder sites typically results in freezing damage, and they grow conservatively and more slowly than the climate would allow if transferred to warmer sites. Forest plantation productivity is commonly in the range of 3 to 4 m³/ha/year, rising to 7 to 8 m³/ha/year with favorable sites and/or good forest plantation management. Growth rates of 17 m³/ha/year have been reported for Picea abies at Westerhof in Germany.

Thus, although the principles of domestication were accepted and practiced by Europeans for over 5 millennia, the indigenous forest tree species were not easily amenable to domestication. Furthermore, most forest-tree species which might have been received from the Fertile Crescent or the Far East were little or no better, either at home or when moved to Europe. Interestingly, rather than being domesticated as highly-productive wood-producing enterprises, European plantation and indigenous forests became instead the almost mystical preserves of a previous culture. Traditions associated with such things as hunting deer and gathering mushrooms are afforded great value, and these services rank high among those provided by European forests.

During the past century, Douglas-fir (Pseudotsuga menziesii) and two poplars (Populus deltoides and P. trichocarpa) from North America have been added to Europe’s forest plantations. Wood productivity has averaged about 18 m³/ha/year for Douglas-fir, even though many forest plantation sites were mismatched with planting stock of inappropriate provenances (Douglas-fir is also sensitive to provenance transfer). The poplars are generally clonally deployed as hybrids with the better-rooting indigenous European Populus nigra. The intensively-managed poplar plantations produce wood in the 20 m³/ha/year range. Other North American members of the Pinaceae, particularly Picea sitchensis and Pinus contorta, have been important additions to northwestern coastal and northern interior forest plantations, from Ireland to Sweden. Provenance variation is important for these species as well. When the right provenances of those species are planted in the right places, their wood productivity is 30% or more greater than that of the local European indigenous spruce and pine.

During the last 50 years, two members of the Cupressaceae (recently Taxodiaceae), redwood (Sequoia sempervirens) and giant sequoia (Sequoiadendron giganteum), have been planted in western and southern Europe with some remarkable successes. Trees in the Cupressaceae have a more open timing and control of growth cessation than do those in the Pinaceae, such that provenance differences are relatively smaller, and clones are often broadly adapted to a variety of sites and locations within the warmer less-continental parts of Europe. Wood productivities of 20 to 30 m³/ha/year are achieved in European giant sequoia plantations, with 44 m³/ha/year well documented at one 80 year old forest plantation in Belgium (Libby, 1981). Redwood commonly achieves 30 to 40 m³/ha/year, in some cases recorded over three full rotations, with 54 m³/ha/year at one French forest plantation. One may wonder what the course of forest-tree domestication might have been, had those species been indigenous or available to curious Europeans when ideas about domestication arrived there about 5 000 years ago.

3.6. Colombia

In 1982, Smurfit Carton de Colombia (SCC) depended completely on wood from an indigenous tropical forest, which was growing useful wood at 3 to 5 m³/ha/year. To obtain a more-uniform raw material for processing, and also with a sensitivity to increasing concerns about logging in tropical forests, SCC began a major project that converted cattle pasture to forest plantations. The eucalypt seedlings in these forest plantations have grown at 25 m³/ha/year, and the selected clones at 40 m³/ha/year. Since 1994, 100% of SCC’s wood needs has been supplied from forest plantations, and the Bajo Calima indigenous forest concession has been returned to the Colombian government. The relative harvest productivity of the SCC forest plantations is, at minimum, 5 times that of the indigenous forest for seedlings, and 8 times its harvest productivity for the clones. In the SCC pulp/paper mills, the eucalypt wood has 30% greater efficiency (pulp yield) than the species mixture of tropical-forest wood it replaced, creating an even higher ratio in favor of the forest plantation source of wood (Wright 1991, 1992).

3.7. USA

3.7.1. California

The state of California has some of the best forest species, forest sites, and climates for growing forest trees on Earth. Until about 1950, California was wood self-sufficient, extracting most of the wood used locally from its magnificent indigenous forests. The idea of forest plantations had not caught on then, nor has it yet. Rather, some of the conservation and later environmental organizations, largely led by people of recent European culture, have instituted some European ideas into California forest policy.

These organizations are generally opposed the establishment of forest plantations, and have worked effectively to restrict or forbid wood-harvest on large areas of California’s forests. Those forests are instead reserved for a variety of other values, including watershed protection, wildlife habitat, and recreation. Interestingly, as in Europe, some of these values seem mystical, and/or rooted in the hunting-and-gathering traditions.

Secondly, this author believes that California is, in an imperialist manner, using its economic and political power, to acquire wood. A decade ago, California had to import over 60% of its wood and wood products, and it has instituted no policies to reverse that trend. As to its future, one can only wonder.

In spite of this grim picture at the policy level, there are some forest plantations in California, and others are being established. The current planting is mostly done by the private sector, but some is done on federal lands following extensive stand-destroying methods. A thin layer of research is accumulating about them. Similar to the Australian research, a series of “Garden of Eden” trials of Pinus ponderosa is being followed. These California trials investigate the main effects on tree growth and its underlying physiology of differences in soils, climates, control of competing vegetation, fertilizer applications, and insect control, and the interactions among these variables. Ten-year results indicate a doubling or better of early growth at most sites by the best treatment combination (usually herbicide plus fertilizer), as compared to the untreated controls. On good sites, a 20+ m³/ha/year productivity over the first 50 years seems attainable with good management inputs (Powers and Reynolds, 1999; and May 2000 communication with Powers). Although low soil moisture became a dominating factor at all sites studied, irrigation was not a treatment and thus its effect was not estimated.

3.7.2. Second generation seed orchards of Pinus taeda

The impact of tree improvement on forest productivity has been substantial through the two cycles of breeding, testing and selection completed by the North Carolina State University- Industry Cooperative Tree Improvement Program. Trees grown from seeds of first-generation seed orchards have produced 7-12% more volume per hectare at harvest than trees grown from wild seeds (Talbert, 1982). With additional improvement in value from quality traits (stem straightness, disease resistance, wood density), the estimated genetic gain in value from first-generation breeding is about 20% (Talbert, Weir and Arnold, 1985). Second-generation seed orchards are now producing more than 50% of the total seed harvest in the region. Progeny test data from second-generation seed orchards are now available to provide genetic gain estimates.

Intensively managed forest plantations of loblolly pine, employing the best genetically improved planting stock and best silvicultural practices, are believed to be the most effective strategies to meet future demands.

Table 1. Predicted average growth gains (%) for 8 year height gains and 25 year volume gains of second generation Pinus taeda (loblolly pine) seed orchards for different geographic regions. Gains are estimated as the percent difference over unimproved check lots.

Source: Li et al., 2000.

With the 7-12% more volume per hectare at harvest from first-generation, and 17-30% more volume per hectare at harvest from second-generation than trees grown from wild seed, the impact of tree improvement on forest productivity has been substantial through the two cycles of breeding.

Genetically improved stock has not only demonstrated outstanding growth, it has also had lower infection from fusiform rust, typically 20-25% below the unimproved controls. With additional improvement from quality traits (stem straightness and wood quality), the realized genetic gains in value are likely to be significant (Li, McKeand and Weir, 2000).

3.7.3. Gum yields of Pinus elliottii

Research to breed a high gum-yielding strain of Pinus elliottii was initiated as early as 1941 by US Forest Service. High-yielding trees were identified and selected, within one year finding one dozen trees (phenogypes) which produced 2-2.5 times as much gum as did average trees. While efforts to root cuttings at the time failed, it was demonstrated that growth characteristics and gum yielding ability were genetically controlled. In 1943 scientists decided to cross-breed the selected high gum yielding plus trees using controlled pollination. Seeds from the resulting families were then outplanted in replicated test plantings (1946). By 1950, over 1000 Pinus elliottii plus trees had been selected for superiority in gum production. Results by 1956 were spectacular: the progenies of high-yielding parents produced from 50-100% more gum than did those of average parents. Some individual trees produced several times as much gum as did average trees in wild stands. Between 1964 and 1972, it was found that the superiority of progeny from high-yielding parents fluctuated between 77 and 106%.No appreciable differences between provenances were found in gum yield.

Seed orchards were established, resulting in progeny which yielded 1.5-2 times as much gum as the average trees, as well as increased amounts of wood, tall oil and turpentine, when harvested for pulpwood. It was subsequently estimated that if the best one-third of 100 selections were chosen for use in seed orchards on the basis of progeny tests, genetic gains would be at least 50% in gum yield and 25% in volume growth. Appreciable gains in stem straightness, crown form, were also expected. Seed in commercial quantities would be available within 10 years.

With the development of high gum yielding strains efforts were started to apply more intensive cultural practices than those normally used when growing forest trees. In 1958, irrigation, fertilizer and cover cropping were applied to an experimental gum orchard. Work was also done on gum composition of 150 trees, including clones and families of known yielding ability. No correlation with gum yield was found, but strong variation was found among individual trees. For example, gum from the cortical tissue of branch tips was discovered to have five major constituents, with the amounts often varying from less than 10% to as high as 70%. Investigation revealed that the quantities of most constituents were inherited- which led to work on breeding for specific composition. It was shown that at least four of the five major monoterpenes in gum from cortical tissue were simply inherited, through single genes. Regarding the more important stem gum it was found that trees of the same genotype but different ages differed in gum composition; this temporarily halted selection for stem gum in the program. However, subsequent studies showed that the determining factor was distance of the sample from the base of the crown and, based on this finding, the selection program was continued.

Work was commenced in the 1970s to develop multiple “strains” which combined high gum yield with such traits as rapid growth, improved quality and yield of wood, disease resistance (Squillace, Dorman and Mcnees, 1972).

Subsequent decrease in demand for natural gums, used mainly in the naval stores industry, slowed and finally terminated the program. However, interesting lessons can and should be learned from the experiences gained.