Bruce J. Zobel
BRUCE J. ZOBEL is E. F. Conger Distinguished Professor of Forestry at North Carolina State University in the United States.
Some benefits of tree breeding
Almost daily one is reminded of the possible crises we may face as the result of an increase in world population and the overall improvement in the standard of living. The concern is nearly always about limitations of the food supply, a recognized and very critical problem. Having enough food alone, however, does not ensure a satisfying existence - products of the forest are a key ingredient of the good life compared to mere subsistence living.
The greatest resources in the world are people and land and the destiny of the human race is determined by the way a large proportion of the world's land areas is clothed in forests of various types; thus, much of the responsibility as to whether we live fully or merely subsist is in the hands of those whose job it is to manage forest lands. We are dealing with an inexhaustible and renewable resource provided by nature. We foresters are aware of our responsibility to manage it wisely so as to obtain the maximum value to mankind while still making sure the forest resource is continuously improved and not depleted or destroyed.
One characteristic of a developing society is its increased usage of fibre products, chief among which is wood in its many forms. It is a certainty that demands on the world's forest lands will become greater while the area available for forest production will decrease. The question facing us is not whether to use the forest resource but how to use it wisely for the greatest benefit to man in the long term. If we as foresters fail, not only will our descendants be deprived of the opportunity for the "good life" and must lead a life of mere subsistence but there is doubt that they can even survive.
There are many challenges to those who manage forest lands; two of the most important are:
First, the forest land resource is finite and foresters must use what is available completely and efficiently while still maintaining it in a renewable state. The current wastage of usable timber plus locking up the renewable forest resource for essentially no use to society is inexcusable and a sin toward mankind. The utilization of forests can vary from wood products to chemical and energy production, to recreation, to watershed management; no one use is so all-important that it relegates all others to inferior positions. Because of the renewable nature of the forest resource, the same goods and services will be available after utilization as were present before if proper management is practised.
Second, wise use of the forest resource does not imply keeping it in exactly the same state as it was prior to management. Nature's "objectives" are not always compatible with the best interests of man; a forester's mission is to make the forest land more productive of the goods or services it is most suited to supply. Sometimes this only requires retaining the forest in its original state, but usually change is required. A surprisingly high proportion of the world's forests have already been greatly (and unfortunately sometimes irreparably) changed by men's past activities in the form of fire, overgrazing, exploitation without regeneration - and, yes, in a few instances, even by overprotection. We, as foresters, have a primary responsibility to put unused or partially utilized lands into production. This includes managing already productive lands so that they can become even more productive. Most forest land in the world can be improved by sound management but foresters have a most difficult task to convince laymen (and unfortunately sometimes other foresters) that the best action is not "to leave the forests as nature made them "or" the best action is no action."
To be successful in their management efforts, foresters must learn much more about the biology of forest growth and development. They must become skilled practicing ecologists. A forest is a dynamic, ever-changing complex biological system, and continuous management is necessary or it may soon no longer be ideal for the objective originally intended. It is sad, for example, to observe the consternation and disillusionment of one who has "preserved a virgin stand of timber for perpetuity" when he sees the old trees die and the idyllic, parklike vista become filled with invading briars, brush and small, unwanted, tolerant trees. Only with management could the original condition be maintained.
Although I am acutely aware of the many uses and services from forest lands other than timber production, including recreation, aesthetics, water quality and others, I must concentrate on one major forest product to meet space requirements for this paper. Since my main expertise is in growing trees to produce timber and cellulose, the following discussion will concentrate on this area, although many of the principles will apply to all aspects of forest land management.
There is a tendency for foresters concerned with timber production to specialize either in utilization and harvesting or in the general area of forest management. This is the wrong approach and we never will obtain the full timber production from forest lands until there is a "marriage" of all expertise, a happy marriage where all contributions are together for the common goal. If, for example, logging is separated from silviculture, great inefficiencies will develop; what the silviculturist can or cannot do is strongly influenced by the logging system applied prior to regeneration. Careless logging can so drastically change the site potential and reduce site index that the strain or species initially growing in the area is no longer suitable. It is inexcusable for the silviculturist to be faced with major problems limiting regeneration and future growth just because a logging method harmful to the site was used through ignorance, lack of concern, or economic pressures.
In the same way, methods of forest management must be used to supplement each other. Thus, genetics without good site preparation or competition control will be ineffective while fertilization without use of the best genetic stock or site preparation can only be partially successful.
In its broadest sense, genetics is only another tool of silviculture used to obtain greater production from forest lands. Considered alone, genetics verges on the academic; used along with proper site preparation, competition control and fertilization, it is the key to maximum production of timber from forest lands. Even though it must be viewed as a silvicultural tool, genetic manipulation of forest trees has certain unique characteristics:
· A genetic change is "permanent" in that it need not be repeated once or several times during each rotation, such as does fertilization, competition control, or site preparation.· As the most productive forest lands are converted to agricultural or other uses, new strains of forest trees can be developed which are adapted to currently marginal or sub-marginal sites; this will enable maintenance or even expansion of the productive forest land area. Similarly, strains for special products can be developed.
· Most insect or disease pests can be efficiently controlled only through developing tolerant strains of trees. Even when controls are known they often are too expensive or difficult to apply or are considered to be too ecologically dangerous to use over extensive forest plantations.
· Through the eons, nature has developed numerous types of trees with greatly differing genetic potentials. It is the responsibility of the tree breeder to recognize, refine and use these for the benefit of man. With forethought and planning the bulk of the gene base can be preserved for new needs that might develop in the future.
· Through selective mating and hybridization it is possible to create "something new," trees with characteristics not available from nature. This ability to tailor-make trees is gaining increased consideration as the variability present in natural forests becomes more widely exploited and ultimately eroded in selective breeding programmes.
Development of desired characteristics through genetic manipulation has given the forest manager a most useful, powerful, and efficient tool to add to other silvicultural methods at his disposal. In certain problem areas the tree breeding approach has revolutionized the thinking and methodology of the forest manager.
The current trend to establish fast-growing conifers and hardwoods in plantations in the tropics will increase.
Because of ease of establishment, emphasis has been on planting on grassland or scrub hardwood sites; however, replacement of tropical hardwood forests by plantations on the most suitable sites is rapidly gaining momentum. In either case, exotic species are generally used, presenting a unique opportunity for the use of genetic manipulation; in fact, success or failure of tropical plantations is more dependent on proper application of genetic knowledge than on any other factor.
The forester contemplating establishing fast-growing plantations in the tropics is, of course, faced with a decision as to which species to use; of equal importance is the decision as to which geographic source is most suitable within the desired species. Seed source is more critical to success in the tropical areas than in the more temperate forest regions. Once species and source have been determined, then improvement by conventional selection and breeding is necessary if maximum timber production is to be obtained.
MATURE HARDWOOD STAND GROWING IN A SWAMP there is much to be learned
A problem often requiring major genetic manipulation relates to pests that will attack exotics. Plantations in the tropics may be pest-free for a few or even for many years, but a certainty is that either a native pest will adapt to the exotic or a pest of the exotic in its natural range will somehow follow the species into the new environment. Usually the only effective way of combating such pest is to develop trees that are genetically tolerant.
A most pleasing recent trend ha been the change of attitude by key foresters and administrators regarding the place of tree breeding in forest operations. Initially many considered it to be research, something with little potential for practical usage. During the past 10 years this attitude has dramatically changed, and many industrial, as well as governmental, programmes now include tree improvement as an integral part of their forest management operations.
One major reason for acceptance of tree breeding in forestry is that it has proved to be a good economic investment. Every economic study of the value of tree improvement with which I am familiar (and that has been many) has shown that genetic manipulation of forest trees yields excellent returns on the investment. Several analyses have concluded that tree improvement is the best possible investment in the whole forestry enterprise.
Tree breeding programmes are well developed in several parts of the world, with advanced-generation breeding already under way. The most urgent need for expansion of effort is in the tropical areas where so much forestry activity is now taking place. For example, seed of species such as Pinus caribaea is in short supply and genetically improved seed is unavailable. Despite its importance it is often not possible to obtain seed from the correct geographic source and much planting is being done using ill-adapted stock. This poses grave danger when large planting programmes are developed and then abandoned, because of failure caused by use of the incorrect seed source. Such a catastrophe can reduce interest and faith in forestry as a sound investment, and several examples of an adverse reaction which set forestry back many years could be cited. The seed problem for tropical areas is especially difficult because it is necessary to cross boundaries of one to several countries if success is to be achieved. With fast-growing species the payoff from the use of genetics will be especially large and rapid if the considerable difficulties can be overcome by means of a cooperative effort.
There is no question that the future of the application of genetics to forest trees is very great. There will be expanded and better supported efforts throughout the world as the need to increase yields from forest land becomes more widely recognized. In some areas the applied programmes are beginning to outstrip the needed base of fundamental information, with the result that certain inefficiencies are developing. Thus, one of the major needs in the future is a greater emphasis on supportive, basic studies necessary to undergird the application phases of tree breeding. The days of straightforward selection and seed orchard establishment are drawing to a close in a number of areas and more sophisticated developmental techniques will be required if tree breeding is to continue making gains without interference from the adverse effects of related matings.
There is no question about the need for increasing emphasis on fast-growing plantations, especially as exotic plantation forestry intensifies. Another urgent need is to work with indigenous tropical species, some of which appear to have outstanding potential although little is known about their silvicultural or genetic characteristics. The huge area of the tropics with plentiful rainfall and soils generally suited for forest production must contribute its share to the welfare of man. In general the hardwoods as a group have been neglected, although progress in breeding the eucalypts has been outstanding.
New methods and new techniques tree breeding must be developed; for too long we have followed the methodology used with agricultural crops. Trees present unique opportunities and advantages if we learn to develop them correctly. As an example, much of the quantitative theory on which forest tree breeders rely is based upon control of important characteristics by single or few genes. Yet many of the most important tree characteristics are determined by complex genie and allelic interactions and the developed theory can only be partially effective. Great emphasis is already being placed on ways to speed up generation turnover and to develop good methods of obtaining juvenile-to-mature correlations. Once accomplished, breeding results and gains per unit time can be greatly improved.
A most important trend is the increase in efforts to develop trees that will produce a useful crop on marginal or submarginal forest land. Land-use pressures and environmental controls require change in the land area that will be used to produce forest products. If forestry is to supply its share of the world's fibre needs, new genetic strains must be tailor-made for currently marginal areas; with the uncertainty about the future cost and availability of fertilizers, strains of trees need to be developed that will grow satisfactorily on soils of low fertility. The success in developing special strains of trees suited to difficult conditions has been outstanding. Directly related to this, an increased tempo toward breeding for resistance to pests is sure to develop.
There will be greater efforts and demands to develop trees better suited for urban usage or for amenity forests. Methods and objectives will vary considerably from breeding for forest production but, because of the high value of the individual tree, techniques can be used that are now viewed as unsuitable.
During the past several years much interest has developed toward using wood in nontraditional ways. Methods are now known to efficiently produce petroleum derivatives, plastics, and sugars from wood. No one yet knows whether manufacture of such products from wood will become generally operational, since it is dependent on the many vagaries of economic conditions, petroleum prices or other factors. If these uses of fibre develop, a new emphasis on cellulose production per se will become evident. We have already been contacted several times by organizations interested in the most efficient way to supply cellulose, regardless of the form of the plant which produces it.
A major effort of tree breeders in the immediate future will be to conserve the genetic base necessary for long-term and continued progress. Forest trees have a very rich store of varied gene complexes that must be preserved for future generations. Erosion of the genetic base will not result so much from breeding programmes per se but from indiscriminate exploitation of the forest resource. Conservation of the gene complexes within a species can be done by several methods but all are expensive. Care must be taken to avoid the panic measures promoted by preservationists in which nonsense laws, rules or regulations are enacted in the guise of gene conservation. This has resulted, for example, in removal of huge areas of tropical hardwoods for use as timber products. Rather than locking up such forests, we need to learn how to use their products for society while at the same time preserving the best of the tremendous store of available genetic variability. It is the duty of everyone involved in tree breeding to do his share to assure the conservation of desired gene complexes.
GRASSLAND BEING PLANTED TO Pinus caribaea changing horizons
As the world population and standard of living increase, greater demands will be made on all benefits from land. Demand for wood per se will greatly increase if society is to satisfy its needs for a better standard of living, of which fibre is an integral part. As forest land becomes diverted to other uses, a major need will be to increase production on the land available and to develop strains of trees for currently marginal and submarginal sites. This can be done by better utilization combined with better forest management and silviculture. One of the most effective tools of the silviculturist is to use the variation found in forest trees through tree breeding programmes; however, maximum gains can only be achieved if all the tools of silviculture are used to supplement each other. Operations in tree breeding are being greatly accelerated as the gains achieved and good economic returns are recognized.
There is a special need to develop genetically improved material for fast-growing plantations of exotics in the tropics. Seed of the proper geographic source is difficult to obtain and very little genetically improved seed is available. A cooperative approach which crosses national boundaries is essential if this most important endeavour is to be successful.
The future development of tree breeding needs emphasis as follows:
· More supportive basic research is essential if the applied programmes are to proceed with the desired speed and efficiency.· There needs to be much more effort on improvement of geographic source and individual tree characteristics for fast growth plantations in the tropical areas.
· New techniques need to be developed so that tree breeders are not so dependent on methods developed for agricultural crops, many of which are not suitable for the gene complexes which control important characteristics in forest trees.
· There needs to be a greatly expanded effort to develop trees for sites now considered marginal or submarginal; a companion effort is to develop strains tolerant to pests.
· If nontraditional uses of cellulose such as for plastics, sugars or energy become generally operational, a great emphasis will deal with the production of maximum amounts of cellulose, regardless of the form of the plants which produce it.
· Major efforts will be needed to conserve important gene complexes which are necessary for continued and expanded progress in tree breeding.
Forest tree breeding has developed rapidly but the horizons for the future appear to be almost limitless. It is a most important tool to help members of society enjoy the good life rather than exist on a subsistence level.
