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Forest Trees (1991)

Chapter:4 Conservation and Management of Tree Genetic Resources

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Suggested Citation:"4 Conservation and Management of Tree Genetic Resources." National Research Council. 1991. Forest Trees. Washington, DC: The National Academies Press. doi: 10.17226/1582.
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4 Conservation and Management of Tree Genetic Resources Knowledge of the structure of genetic variation in species is needed to make decisions about how to protect the genetic diversity of trees. Without that knowledge, the safest conser- vation strategy requires conserving virtually everything, without any priorities. Some aspects of the distribution of genetic variation are known, however, and that information, while incomplete, can help guide the development of useful conservation strategies. CONSERVATION AND MANAGEMENT STRATEGIES The structure of genetic variation within and among species is an inherent feature of the evolution of forests and must therefore be considered in developing any conservation strategy. It is also directly and indirectly influenced by many human activities, from incidental and unintended effects to intensive management and breeding. Breeding can create greater diversity among populations and can enhance the utility of the genetic resource by managing advanced generations of diverse breeding populations. In contrast to agricultural crops, forest trees have long regeneration cycles and generally grow under less intensive field cultivation. Their breeding, therefore, requires greater use of wide sources of variability. Less intensive activities than breeding can still conserve the present distribution of genetic variation, or can guide the future evolution of at least some parts of forest ecosystems by affecting natural regeneration. When conserving trees in situ, it may be necessary to incorporate 73

74 / Forest Trees very large areas of land in order to conserve the gene pool adequately, because of the potentially wide geographic distribution of diversity and the complexity of the mating systems involved. Merely counting num- bers of trunks is an inadequate guide to determining the effective population sizes of species, and merely counting species is inadequate for determining the existence of the genetic resources of key plant and animal species. Knowledge of the requirements for perpetuating most tree species is generally meager, and ability to organize conservation programs is low. As a result, conservation is often reduced to preserving areas in centers of species diversity in the hope that genetic diversity and differentiation are also conserved. Clearly, this pragmatic approach is necessary, but by itself, it is an insufficient step in genetic conservation and only adequate as a short-term contingency measure while more satisfactory conservation strategies are developed. A few species, such as Picea abies (Norway spruce), are already included in broadly sampled collections. Others, such as Pinus densiflora, have such little variation among populations that there is little current concern for conserving their genetic variation. For most species, how- ever, genetic variation is not well conserved, and certainly, not all significant variation is included in established genetic conservation or breeding programs. Further, for scores of species, ecogeographical surveys are still needed, at least to target populations for breeding. Such surveys are also needed for continued monitoring of the distribution of genetic variation to trigger warnings about the need for management interventions. If the sampling problem is solvable, then an array of management techniques exist that differ not only in the details of their execution but also in the conditions under which they are necessary or particularly useful. At one extreme of simplicity, a species may exist in a state of homogeneity for all gene loci so that any sample of sufficient size would capture all alleles. In such situations the breeding can be straightforward, based on a single selection objective. Such a situation may exist for a few species whose natural variation may be very low. Also, for genetically depauperate species, that is, species in which little useful genetic variation exists, any equivalent size sample is as sufficient as any other sample. In such cases, simple storage and propagation programs are sufficient. For almost all tree species, however, experimentation shows that genetic variation is high. But not all species have to be developed for all uses; hence, if the objectives are limited, finite conservation programs can be more readily defined. Some species exist within secure collections that contain a wide sample of the extant genetic variation and little

Conservation and Management of Tree Genetic Resources / 75 further collection is needed, although better maintenance may be required. If species are classified according to the objectives of a forest management program, those whose values lie exclusively in nonprod- uction functions can only be managed in situ and are primarily repro- duced by natural regeneration. For most of these species, no direct management interventions are feasible, but some forms of forest man- agement (by regulating removal of trees or by preventive maintenance) can affect population sizes and structures, as well as their genotypic distributions, and thereby maintain the genetic variation needed for population viability and general evolution of the species. It is also possible that introducing populations of key species into reclamation areas or stand clearings could affect the evolution of the local ecosystem. For most of the tens of thousands of species whose values are unknown, conserving genetic variation also depends on maintaining in situ stands. The adequacy of such programs for conserving nonpro- duction functions would therefore be the primary focus for these species. Although some of these species might eventually be found to be amenable to production forestry and some will be found to have traits of use for timber, medicinal, or other products, their interim maintenance will largely depend on the quality of in situ programs. Seed storage may be a feasible means of conserving sampled variation, and it may be necessary for species in endangered habitats. The cost of sampling, collecting, and storing more than a few hundred or thousand species may be too high, however, to justify allocating scarce funds for this purpose. Moreover, storage methods are not known for seeds of most species. IN SITU CONSERVATION In general, in situ conservation methods share three characteristics (Food and Agriculture Organization, 1984a): · All growth phases of a target species are maintained largely within the ecosystem in which they originally evolved. · Land use of the sites (e.g., agroforestry) is limited to those activities that will not have detrimental effects on habitat conservation objectives. · Regeneration of target species occurs without human manipula- tion, or intervention is confined to short-term measures to counter detrimental factors resulting from adjacent land use or from fragmen- tation of the forest. Examples of manipulation that may be necessary in heavily altered ecosystems are artificial regeneration using local seed and manual weeding or controlled burning to suppress competing species temporarily.

76 / Forest Trees WHY TROPICAL TREE SPECIES MAY NEED LARGER RESERVES Protium occultum Daly is a rare tree known only from Manaus and Jari in Brazil. It was first collected in 1985. The species belongs to the Burseraceae (frankincense) family, which throughout the tropics provides sources of resins used for illumination, caulking agents, and medicines. Credit: Douglas Daly. Ample evidence ex- ists that canopy trees in most forests, including tropical lowland wet forests, are strongly outbred (Ashton, 1969; Bawa, 1974, 1979; Bawa et al., 19854. However, population densities of large trees, which con- stitute the most impor- tant forest genetic re- sources, in tropical lowland wet forests are extremely low. In a tropical lowland wet forest in Panama, for example, Hubbell and Foster (1986) found that one-third of all plant species with individuals larger than 1 cm dbh (diameter at breast height) were repre- sented by only one adult per ha in the 50-ha plot they sampled. Assum- ing that these species are evenly distributed (many are not), an area of 20 km2 would be required to encompass 2,000 individuals. For the rarest tree species in southeast Asian tropical wet forests, Ashton (1981) estimated that an area of 20 km2 would be required to encompass 200 individuals. By extrapolation, 200 km2 may be needed for 2,000 individuals. Unfortunately, in many regions the areas earmarked for conserving certain vegetative types or forest genetic resources are well below the minimum sizes estimated above for a single species in contiguous areas. Most species are not uniformly distributed, and temporal variation within any possible reserve area may also exist. Therefore, it is logical to consider the minimum area required to maintain genetically viable populations in one or several reserves. Moreover, rare species may not, in fact, be rare everywhere. Thus multiple reserves may conserve more rare species than single reserves. Even so, the reserves would have to be very large for some species.

Conservation and Management of Tree Genetic Resources / 77 Key requirements for in situ conservation of threatened or endangered genetic resources are the estimation and design of minimum viable population areas for a target species. To ensure conservation of sub- stantial genetic diversity within a species, multiple reserves must be created, the exact number and size of which will depend on the distribution of the genetic diversity of the selected species. The pro- motion of the continued maintenance and function of an ecosystem under in situ conservation depends on an understanding of several ecological interactions, particularly the symbiotic relationships among plants, pollinators, seed dispersers, fungi associated with tree roots, and the animals that live in the ecosystem. M~nnnum Viable Population Size The concept of minimum viable population size implies that a population in a given habitat cannot persist if the number of organisms is reduced below a certain threshold. It is a complex concept because there is no recognized minimum viable population size for most species. Whether a population of a given size can persist depends on a number of random or unpredictable demographic, genetic, and environmental events (Gilpin and Soule, 1986~. Moreover, population size varies with such attributes as life history, particularly generation time and the breeding system, and the spatial distribution of resources (Gilpin and Soule, 1986~. Nevertheless, minimum viable population sizes have been estimated for several groups of organisms on the basis of genetic criteria (Franklin, 1980; Soule, 1980~. Three broad approaches to estimating minimum viable population size have been taken. One approach is to estimate the effective popu- lation on the basis of ability to withstand loss of genetic variability due to small population size. For animal populations, it has been estimated that loss of genetic variability due to inbreeding can be avoided if the rate of inbreeding per generation, F. is kept below 2 percent (Franklin, 1980; Soule, 1980~. If F is known, the effective population size (Ne) can be calculated by the equation: 2Ne Thus, the effective population size of 25 would be sufficient if 2 percent inbreeding per generation is acceptable. Taking 1 percent as a more conservative estimate of a tolerable level of inbreeding in animals, Frankel and Soule (1981) calculated the minimum population size to be 50. This effective population size is in general sufficient for short periods

78 / Forest Trees (i.e., a few generations), after which the captive populations can be released in the wild and variation might increase. However, the applic- ability of this approach as well as the estimated effective population size to forest trees is questionable. Such mathematical approaches can oversimplify more complex biological realities (Ewens et al., 1987~. Although the population sizes are on the same order of magnitude as those derived from ecological models, the effects of demographic randomness on the total sizes needed are larger due to the independent factors of inbreeding and random loss in the population. The second approach is to estimate effective population size on the basis of the number required to maintain the evolutionary potential of the population. It has been estimated that if Ne is 500 individuals, a panmictic population one in which mating is entirely random is not likely to lose genetic variance due to drift and can retain enough variation to respond to altered selection pressures (Franklin, 1980~. Assuming that the ratio between census numbers N and Ne is 3 or 4 (Soule, 1980), the minimum population size then becomes 1,500 or 2,000 individuals. Both the N and Ne specified above are for outbreeding, monoecious species. The third approach is based on calculating the population size that will minimize the sampling loss of alleles that occur in low frequency. Namkoong (1984) has estimated that in species with known levels of inbreeding and population structure, a sample size of 1,000 will keep the probability of the loss of an allele that occurs at the frequency of 0.01 at a particular locus below 0.01. An increase in the number of loci at which desired rare alleles occur will increase the number of individuals required to minimize the probability of loss, but at a much lower rate than by decreasing the frequency of the desired allele. The sizes mentioned above are based on the minimum population sizes required for evolutionary flexibility and, therefore, continued survival. However, minimum population size is a probabilistic concept and not a fixed number, and can be affected by biological, environmental, or genetic events (Soule, 1987~. It specifies a population's probability of becoming extinct under certain conditions. That probability depends not only on the past evolutionary history of the species and its current genetic structure, but also on demographic and environmental random- ness (Gilpin and Soule, 1986~. The minimum population size, therefore, is likely to differ among species and among habitats for the same species. Number of Reserves and Sampling Strategy Although much of the literature is couched in terms of conserving particular populations, in situ conservation in reality involves preserving

Conservation and Management of Tree Genetic Resources 1 79 whole communities. The number of populations and species that require some protective measure in the wild is so large that it is impractical to design in situ conservation programs on the basis of individual species and their populations. There may exist well-correlated sets of co- occurrences of species that can, for immediate conservation purposes, be considered to be distinct assemblages, if not communities. In areas where several species are being simultaneously conserved in a reserve, a problem exists in ensuring that the number and distribution of such populations of the contained species are adequate for maintaining genetic diversity in either single or multiple reserves. Without infor- mation about the distribution of genetic variability, it is difficult to assess the number and distribution of populations in one or more reserves that might be required to encompass much of the genetic diversity. This lack of information also constrains determining the level of migration for various species. For some species this may be close to zero while for others it may be high. The capacity of individual reserves to preserve evolutionary dynamics within their individual borders can have signif- icant effects on migration. Because forest trees generally show interpopulational variation in some traits, several small reserves spread over a large geographical area may conserve total genetic diversity more effectively than a single, large reserve. Theoretically, and for easily managed species, the viability of single populations may be maintained with effective population sizes of 50 to 100 reproductive individuals, and it would be possible to contain a total of a few thousand in as few as 50 or so reserves. For many tropical tree species, however, areas with 50 to 100 individuals may be too small to maintain the integrity of key mutualistic interactions and to preclude instability due to random events. Larger populations must then be maintained, or means must be developed to augment seed and pollen migration, such as planting or providing corridors for seed and pollen dispersers. Thus, a reserve system that is adequate for any one species may be insufficient for others. To determine the adequacy of a reserve system, an inventory strategy can be used. A finite number of species clusters, cover types, or key species could be inventoried and mapped, and the areas required for adequate allele sampling could then be designated. Simultaneously, an inventory of existing reserves and parks could be made to determine the extent to which populations are included within those same cluster categories. A comparison of the sets would then indicate the extent to which populations of those indicator clusters are already included in reserve areas and what other reserve areas are needed for the sampled species. An extrapolation to all species could then be estimated on the basis of the representativeness of the original sample. This approach

go/ ~n~,T~ flacks the population- and allele level detail needed for all species in a cameo p as, hat ~ gum ~ Id ~ idling ~ Lagos of labor genera de~ciendes at the Ovulation level. S<p~g~f~ Ins m~n~ld~d .. . Within Unsexes, populations an be identified in patches of vagina sues. With tab species~bothtempo~landspa~a~lvabiti~ons can affect C^lEC~O~RlE~S FOR CO~\S~E~RVA110s~ AREAS The 1pte~4t~nal UP cation of Nature and Natural RCs~rces ~ ~ ~ ~ ~ . . {1~j Cam ~SS!lll0S ln Slat conservation arms on. the basiso!flP mange it: ~ ' ~ ! ' , , Nag Sac ~~~ were; a/ na tionz1 park; 111, nat~1 Monument / natural . . , ~ .. ~n~; v/ name co~nseradon reserve red nary ~ ,. . ~ ~ ., se~rve/~ildli~ saner are; V, protected Ends Resource Serve; V~11, natural biotic a~~3n~ thro~l~ica1 resere; V111, mul.tipl~e-use management a~re~mana~ed resource alas; 1X, biosphere se~~e; arid X, worlds bedfast site (natural). The mana~e!ment methods tar Bar of those teas {1~, l~I,~lV, and Vll~l~) am pertinent to this discussion and Lucas descriptors are Trend. below. LIZ ~ ;~ O~4~.)~7 ^~f~7 f~ 37~s}.~ ~ Is. C~ff:G~ ~ F. Id Act. ~1ct~re Reserves The objectives of a strict nature rese~e are to protect communizes and species and to maintain datum processes in an undisturbed state in. order to gave ecolo~~lly epe~n~Eve exa~p~s of the natural environment acme ~ wining ~6 arums in a dye and e~u~o~ state and Or scientific study, environmental monitoring find education Such reserves often contain ~gi.~le ecosystems or lip forms, am areas of

Conservation and Management of Tree Genetic Resources 181 genetic structure, but they can be managed to differentiate population segments. To maintain genetic diversity in a single reserve, sufficient numbers of interbreeding but segregated (separate) populations are needed. The above-stated figures on minimum effective population sizes would then have to be inflated if populations are endangered by common threats. Segregated populations may also be required to generate wider variations and to protect species-wide allelic diversity more effectively. Hence, reserves should be large enough or managed important biological or geological diversity, or are of particular importance to conserving genetic resources. Because only natural processes are allowed to take place, without any direct human interference, only monitoring and nondisruptive sampling are permitted. Because extinction is a natural process, for species that are vulnerable such reserves are a resource only as a supplement to other conservation programs. National Parks The management objectives of these types of areas call for protecting natural and scenic areas of national or international significance for scientific, educational, and recreational uses. To ensure ecological stability and diversity, the areas should perpetuate, in a natural state, representative samples of geographic regions, biotic communities and genetic resources, and species in danger of extinction. Such areas generally encompass relatively large land tracts that contain one or several entire ecosystems that are not materially altered by human exploitation and occupation. As for managed nature reserves with secure legal status, opportunities exist for developing minimally interventionist techniques for ensuring genetic diversity in self-sustaining ecosystems. Possibilities also exist for devel- oping genetic diversity in restored ecosystems by introducing certain levels and types of genetic variation. With sustained monitoring, these areas can also serve as a secure collection of evolving populations. Managed Nature Reserves The purpose of managed nature reserves is to ensure through specific human manipulation the perpetuation of natural conditions necessary to protect nationally significant species, groups of species, biotic communi- ties, or physical features of the environment. Scientific research, environ- mental monitoring, and educational use are the primary activities asso- ciated with this category. Although a variety of protected areas fall within this category, each would have as its primary purpose the protection of nature and not the production of harvestable, renewable resources, although the latter might be an aspect of managing a particular area. (continued)

82 / Forest Trees in separate forest compartments to permit independent population development. If selection affects allele distributions, separate popula- tions probably offer greater protection for allelic polymorphisms than do unified populations. The design of conservation programs is still very primitive with respect to ensuring the structural integrity of the genetic system of conserved species in other than the simplest boreal types of ecosystems, if even there. A large degree of genetic redundancy within and among Managed nature reserves can provide long-term security for species by maintaining the ecosystem necessary for natural reproduction or by introducing genotypes from other sources or from populations bred for different objectives. The development of genetically variable populations in seminatural (i.e., managed) ecosystems is a unique but as yet unexplored technique for simultaneously affecting and studying the responses of ecosystems to nonintentional interactions. These areas are often legally secured and, hence, can serve as a long-term, living resource base for the conservation of evolving populations. MULTIPLE-USE MANAGEMENT AREA/ MANAGED RESOURCE AREA This management category primarily supports economic activities, although specific zones may also be designated within an area to achieve specific conservation objectives. Parts of an area may be settled and may have been altered by humans. The goal of this management method is to provide for the sustained development of water, timber, wildlife, pasture, and outdoor recreation and at the same time provide for economic, social, and cultural needs over a long term. The areas are managed on a sustained- yield basis. Hence, they are often closely allied with traditional breeding operations for managing genetic diversity. In contrast to industrial forestry, the objectives of forest management and genetic selection in these areas are not exclusively for industrial profit. The managed populations would at least partially be recurrently selected and could be a diverse living resource. Several programs, such as the United Nations Educational, Scientific, and Cultural Organization's Man and the Biosphere Program, with its "biosphere reserves," incorporate various mixtures of in situ techniques with the objective of ensuring the continued existence of well-protected areas and the continued use of resources by locally affected people. Often, the strict nature reserves are located in a protected zone, and surrounding or adjacent areas are designated for increasing levels of human interven- tion. Such systems can integrate multiple levels of genetic variation between and within usage zones and could provide unique opportunities for experimental genetic management.

Conservation and Management of Tree Genetic Resources / 83 conservation units is needed, at least until more is known about safe levels of loss and how they are balanced by changes in other units. Knowledge of Ecosystem Dynamics and Integrity A key requirement in managing nature reserves is the knowledge of ecosystem dynamics. The minimum viable population size may ensure genetic diversity through generations only if the structure and stability of the ecosystem are maintained. This is true regardless of the number of species that are targeted for conservation. Among the many biotic forces that impinge on community structure and stability is the integrity of the food web in an ecosystem (Pimm, 1986~. The organization of food webs is particularly important for maintaining forest genetic resources in the subtropics or tropics, where the pollen and seed of an over- whelming majority of forest trees are dispersed by a wide variety of animals. The diverse feeding relationships among a multitude of animals and numerous plant species add extraordinary complexity to the web of dependency. Species that provide food resources in the form of pollen, nectar, fruits, and seeds to pollinators, seed dispersal agents, and seed predators may play a critical role in maintaining the structure and stability of the community (Gilbert, 1980; Terborgh, 1986~. In some areas, pollinators may come from distant sources and seed dispersers may migrate from one place to another on an elevation gradient. During the dry season in Costa Rica, for example, pollinating moths migrate from a dry deciduous forest to a wet forest several kilometers away (lanzen, 1987~. In southeast Asian forests, bats fly over many kilometers to pollinate their host plants (Marshall, 1983~. In Amazonia, fruit-eating species (frugivores) may migrate to other elevations during periods of food shortage (Terborgh, 1986~. The populations of seed predators and seed dispersal agents may be regulated by top carnivores, which require a very large area to maintain viable populations. In reserves lacking carnivores, populations of seed predators and seed dispersal agents may increase with concomitant, but unknown, effects on the relative densities of various tree species (Terborgh, 1988~. In brief, maintaining tree populations in a tropical community is contingent on a very thorough understanding of key ecological inter- actions between plants and their pollinators, seed dispersers, and seed predators as well as the spatial and temporal distribution of floral, fruit, and seed resources. The link between pollinators, seed dispersers, and seed predators and their host plants is not the only critical element in maintaining community stability, although pollen-seed vectors and seed

84 / Forest Trees predators play a vital part in plant reproduction. Information on other processes and their effects on community integrity are contained in a series of articles in Conservation Biology: The Science of Scarcity and Diversity (Soule, 1986~. Prospects for Effective In Situ Programs An effective in situ program for genetic conservation has several key aspects: identification of gene pools, selection of specific sites, acquisition and design of the layout and administration of the reserves to ensure the availability of germplasm for use, and management of the reserves in perpetuity. Consideration of the needs of local people must also be emphasized, because in situ conservation techniques can rarely if ever be carried out without the collaboration of the locally affected people. Thus, adjunct programs that provide instruction in the purpose and use of conservation areas are often indispensable, and research is needed on the design of programs and social support structures that can contribute to maintaining in situ stands. Because in situ stands often provide services to various interests, coordination among those interests must also be included in program development plans. This will often require that site selection criteria include ease of management and minimal disruption of local uses. For managed areas, sites must be integrable with multiple local uses and accessible for management and collection activities (Palmberg, 1988~. For many tree species, for example, controlled harvesting or other moderate disturbances are not necessarily threats to viability. The possibilities for translating these concepts into practice are strongly constrained by the diversity of funding sources for conservation activities and by the generally low levels of funds available. Moreover, many agencies, whether their programs are coordinated or not, have different conservation objectives. Hence, no global agenda for species inclusive- ness exists. Only one-third of the biosphere reserves have been inven- toried, even for trees; many other designated areas are not sufficiently well protected to ensure the security of species thought to be contained within their borders, and almost none is scientifically managed to maintain species diversity or genetic variation of the constituent species. In addition, no broad agreement exists on what is expected of local peoples or governments with respect to the conservation agency. Hence, the agency may confront lack of infrastructure support, indifference, or even an adversary relationship with different segments of the public and among sectoral users. The potential conservation utility of these programs has not been realized and may not be for many years.

- ~- - ~- : : : : If ~< If ~ TO Goofy R~ / ~ ,. . . . ..... .. .. . . . . ~ ::::: 1111 Botanical gardens and agog bare ax situ ~nse~~-n sites far 1~1 and introduced tree species. The Arnold .A~o~tum fin jama~i~ Plain, Massachusetts, contains several species of the Onus Ace. or larch (pictured helled, and. other socks Back dodge pant Logon expedibon$Jo ~mpe~te Ions of Asia in the 18~s. Cat: Calvin R. Sperli~ng. ~ SOL CO~10\ in contrast to in Situ methods/ ax site. methods include any of those practices that conserve genetic mat~e~ria~1 outside the natural distribution of the parent population/ and they may use eproducdve matedal of individuals or stands located beyond the site off the paint population Ex situ methods and. matedals include gene banks ~r seed or pollen

86 / Forest Trees and clonal banks, arboreta, and breeding populations (Banner, 1985~. They also include active collections involving shorter-term, temporary storage to distribute materials for evaluation and screening, as well as working collections for breeding. The most common form of ex situ conservation of trees is the living stand. Such stands are frequently started from a single-source seed collection and are maintained for observational purposes. The size of the stands may range from specimens in botanical gardens and arboreta, to a few ornamental trees on small plots, to larger units with scores of trees. Seed storage, another ex situ conservation method, refers to storage of intact seeds in a controlled environment. Under controlled temper- ature and moisture conditions, stored seed of some species remain viable for decades. This technique is the mainstay of germplasm conservation of agriculturally important species, and it is starting to be used for conserving rare tree species. When the viability of stored seeds decreases, the usual procedure is to regenerate the sample in the field. This procedure is impractical for tree species, however, because of the long vegetative period before trees produce seeds (up to 20 or more years), but alternative strategies can be developed. A system of regen- eration stands can be organized, for example, to ensure the continuous availability of sexually mature samples, and vegetative materials can be held in juvenile condition by hedging and other techniques and then allowed to mature quickly when needed. Coordinated sets of materials can then be kept available for any set of stored genotypes. Although collections exist in many independent tree seed banks, the collections are vulnerable because standards of maintenance are often less than ideal and regeneration is lacking or insufficient. Only the seeds with fully orthodox behavior, such as the seed of temperate-zone commercially important genera, store well for a few decades at subfreez- ing temperatures and 6 to 10 percent relative humidity. These include Pinus (pine), Picea (spruce), Larix (larch), Abies (fir), Tsuga (hemlock), Pseudotsuga (Douglas fir), Alnus (alder), Fraxinus (ash), Liriodendron (tulip tree), Platanus (plane tree), Liquidambar (sweet gum), Betula (birch), and Prunus (stone fruits). In the tropics, they include Eucalyptus, Casuarina (she oaks), Citrus (citrus fruit), Gmelina, and some Dipterocarpus and Acacia species. Some species produce recalcitrant seeds that are desic- cation intolerant (cannot survive the removal of moisture), such as Shorea (mahogany) and some species within the genera Quercus (oak), Acer (maple), and Aesculus (horse chestnut) (P. S. Ashton, Harvard University, personal communication, May 1990; Banner, 1990), or that cannot survive low temperatures, such as Quercus and Aesculus in the temperate zone and Shorea (mahogany) and Hopea species in the tropics

Conservation and Management of Tree Genetic Resources / 87 (Withers and Williams, 1982~. Techniques such as cryopreservation of embryos, pollen, and tissue may enable long-term storage of desiccation- intolerant species. Current seed collections are primarily stored for short- or medium- term storage of materials for afforestation and reforestation. Very few programs have long-term objectives, and at this writing, forestry pro- grams have just begun to address the practical constraints of long-term seed storage. With modern freeze-drying techniques, pollen of some species can be stored at a very low moisture content and at subfreezing temperatures. For regeneration purposes, however, this technique requires comple- mentary female structures to enable use of the pollen in seed production. Strategies for the use of seed and pollen in regeneration still need to be defined and implemented. Although pollen seems harder to store than seed for some gymnosperms (e.g., conifers), the constraint may be overcome by further testing and development. Maintenance of living stands as field gene banks is another ex situ method, but its use is currently restricted to highly selected genotypes of species that are of commercial importance, such as those in breeding programs in which graftings or rooted cuttings can be developed into mature reproductive materials. Hence, at present, such trees are hardly to be considered conservation collections. With the use of cuttings, genetic variation in cloning ability is often seen. Cuttings are useful for preserving specific genotypes, obtaining rapid regeneration, and saving genotypes faced with destruction that cannot otherwise reproduce. Tissue culture also has potential to provide a secure conservation method. The technique involves micropropagation (whether meristems, embryos, or other). It requires large investments in development, but if cryogenic storage is developed it provides a secure conservation method. The concept of in vitro gene banks is being tested for selected agricultural crops by international agricultural research centers, and some operational aspects could be widely applicable particularly for facilitating the international exchange of disease-free planting materials (Withers, 1989~. However, tissue culture is still in the experimental stages for most forest tree species. Cryogenic storage, the preservation of biological material suspended above or in liquid nitrogen at temperatures from -150°C to -196°C, has been used for many years as a means of keeping animal semen for breeding purposes. This technology is relatively new to seed storage, and hence, the time limits for storage of true orthodox seeds have not yet been determined. Cryogenic storage of genera with small seeds, such as Eucalyptus, may be cost-effective, and the technology promises

~ / Off ~ Biotechnology provides also far ma!na~ing Mast Me resources: For example, ene5~call~y ~nifo~ plants can ~ Ted in test babes. This (lump of pine ~ plan.tlets was ~e~ne~ted -~m. individual plant cells in tissue c~l~t~re. Credit: u.s. Agency for ln~rnaC~onal ~velop~ent~ ~ssgeneUc da ~ ge then conven~onalseed Comae. ~ ~ even stooge of ~caldb~ntseeds/cos~ far ~rge~seeded spedes,suscepdbLides ~<tan~aLbreakd~n~ and regene=don remain Don nudge problems to be overcome.

Conservation and Management of Tree Genetic Resources / 89 CHOICE OF METHOD The use of ex situ stands for active conservation in multiple and well- secured locations could be applied to many more than the few species used thus far. Such stands could comprise relatively small areas, but they must be a part of a network of areas to ensure the survival and availability of propagules and to provide data on performance over a variety of sites. The design of such conservation stands as active collections is well known, but combining material from such collections with the working collections used in breeding programs and also with various managed areas used in in situ programs would provide a vital link for conserving and using the total gene pool of a species. While this is the underlying principle behind the networks of programs coordinated by the International Board for Plant Genetic Resources (IBPGR) for agricultural crops, there are no global programs for estab- lishing such linkages for forest tree genetic resources. One of the decisions that must be made now is to establish an active forestry program that creates an overall conceptual framework, including much-needed research on several of the above-mentioned technological barriers to safe, long-term seed storage. The knowledge of international organizations, such as the Food and Agriculture Organization (FAO), the International Union for the Conservation of Nature and Natural Resources (IUCN), the IBPGR, and many others, can be of great value in this regard. Forestry scientists will also be needed to convey infor- mation about the unique characteristics of forest species to agricultural scientists in the most efficient manner. Technical and Biological Factors Among the considerations that affect the choice of conservation technique is the fact that the technology does not exist for ex situ storage of many species, and thus, in situ management is necessary until such techniques have been tested and applied. On the other hand, growing trees to sexual maturity takes considerable time and space, as noted earlier, and regenerating populations with an intended mating and genetic structure can rarely be assured. Finally, although viable seed storage is not yet technically or economically feasible for many species, it is feasible for many other species, but it is not yet being implemented. Effective use of conserved populations has exclusively depended on distributing seeds for testing and observation or as genetic material for breeding. A substantial time lag occurs before seeds can be grown into trees useful in breeding or other programs. This situation is also true

~ / ~! ~ : ~ .^a:.~!~:~:::~:::~:' ~sssss:s:ssss~ss:sssssssss:sssssssssssssssss ::::::::S:S:::S::: ::::::::.S.:: ::::S :::.:::::::.S . ... ~C#nese Master explains The Isle golf geld Pence I at ldblgl>~ Spin seed Cam tag Baited Saws Really and slash pines Prig planed ex~n~sively~ in A-a, Asia, gad Labn Beg. CeditF Stanley mu n ashen Larry initial~seed col~cdons~or ~!t~te ~con~servadon stands ale needed.Becauseofthe dmelag,n~eedsforseedsor mabure~trees~usuaDv cannot he met q~ic~y by growing out a population on dernand~as ~ done With an~nuals~.<~Ho~ever,so~ ohe~ives comb achieved by Aider use ofvege~dve propagation techn~u~e~s Belch touId shaken . · . thetimela~gi~sIjvings1and:collecionshave,th~e~efoteybeenth~etechrique of choice for short~to~medi:u m~terni storage needs For the long term (more then 50~years), seed storageis ocean preferred>~b~t it requires the support offing Stands. Lon~>term conservation by seed or tissue storage I~ neat t~si~callvi~sfeas~ble for~manv species and, for those for .. ~ , ~ v~hichi~tsee~>sp~ronn~ising~nofo~rn~alprogram exists. among the ~ol~o{tal~ctorsth~f~rt the dh~oiceof~chn~ueis Me ^ ^ importance ofn.aO~r~1 manna and select~io:ni~nib~e scenic structure of ma~naced Options Far many s~edes/the reproductive processes ~. . . ~ are difficult to control and yet s~on~lv a~Fe(1 oo~u~lahon structure. , ^ . . . ~ Selection ~rcesresu~lting gob multiple env~i~onmentaJs~tresses,com~ perform mutuaLs~,and pathogens nay require the evolution of m ulLple in site populations. With some conse~adon methods, it may be

Conservation and Management of Tree Genetic Resources 191 particularly desirable to allow the population to adapt to a relatively unmanaged ecosystem. In situ conservation is also necessary to conserve communities and ecosystems, and it can be sufficient also for conserving the many plant and animal species associated with those systems. For research purposes and for use in uncontrolled environments, in situ populations are obviously needed. However, when breeding and selection systems are simpler and populations can be managed in controlled environments outside their ecosystems of origin, then breeding, testing, and germ- plasm development can be more efficient in ex situ populations that are developed for controlled-use conditions. Management Factors Among the management factors that affect the choice of technique is the capacity to protect or develop the resource. Given the uncertainty about the extent and distribution of genetic variation and, hence, the capability to target genetic sampling very well, in situ methods may require so many and such large areas that they exceed any reasonable management capacity. On the other hand, ex situ methods are limited by the capacity to store seeds, pollen, or tissue cultures and by managerial capacities to ensure survival and reproduction in controlled plantings. Any in situ or ex situ methods that require large investments in area or effort for long, sustained periods are obviously vulnerable to lapses in control. The susceptibility of in situ methods to gene erosion seems most acute when habitats are threatened, ecosystems are unstable, and managerial authority is weak. Obviously, a great expansion of programs is needed in terms of both structural depth and species inclusiveness, but research on program design is also needed to estimate the effec- tiveness of in situ conservation. Ex situ methods seem of most limited value with species that are still maintained in wild or semidomesticated conditions and where combined objectives, such as in agro- or pastoral- silvicultural systems, can be implemented in one program the very conditions for the forest tree species most often threatened. It seems clear that combining management techniques will always be necessary for any global program, even for a single species. There are also techniques not easily classifiable as in situ or ex situ but that nevertheless form part of the managerial toolbox for gene conservation. When populations become domesticated and form part of a set of breeding populations, they may change from ex situ status to in situ status if they are allowed to develop and evolve within a new ecosystem. The management of seminatural regeneration, with partial control of

92 / Forest Trees parentage or matings between planted and natural stands, is a technique that can be useful for genetic management. It will become more frequently used, at least in temperate forests, in the near future. If in situ conservation stands are too small to ensure their continued evolu- tion, some ex situ stands may be used or developed from the original population and used to regenerate some portion of the in situ stand. For production forestry, more direct gene management is economically feasible and for some of those species that are already intensively and widely used, advanced breeding programs are in place. For these species, ex situ breeding populations may exist in seed orchards. Supplemental populations may have to be made available, however, to ensure the viability of breeding populations for future uses, and those populations can come from either ex situ or in situ conservation stands or collections. The supplemental populations may be bred for enhanced performance for more widely varying environmental conditions (e.g., the predicted global climatic change), or for more extreme trait expres- sions than are currently needed. If even these population sets do not satisfy all of the potential needs for breeding or other uses, or if wider samples are desired for saving low-frequency alleles or alleles at risk for other reasons, then additional populations may be maintained in conservation stands or in stands selected for a wider array of uses. Conservation in situ, however, may require more stands than would be required for efficient sampling of the current diversity. If global climatic change is as rapid as some predict it will be, ex situ seeds or stands might be the only source of materials available for breeding. For several hundred other species that have been described, or are being identified, as potentially useful for production forestry, in situ conservation methods are largely being used if any conservation programs exist at all. For such species, ex situ stands are being developed in research and testing programs. Hence, heavy reliance must still be placed on in situ conservation until a sufficient array of reproductively competent ex situ conservation stands can be secured. Although this management approach would primarily involve tropical and subtropical species, many temperate species are appropriate candidates for similar management. The movement of germplasm from in situ to various forms of ex situ use and conservation can be formalized in provenance testing, but this approach has not been effectively developed for large numbers of species of potential but still unknown value. Some organized systems for broad- scale provenance testing have been instituted by such organizations as the Oxford Forestry Institute and the FAO, but a global strategy for efficient, low-cost, and rapid screening of hundreds of species has not been developed.

Off ~) ~! ~ ~ C~L am / ~ numb Hoper in lndonesib holds a kid~s=~ddli~ one ~jertip.~ About ha of this local s~pedes~ Hill ~ plaints and later Ed for Led and Coitus. Credit: lames P. Blair <~bona1 Geo~c Shies. ~^ ~ OF ~ specie The committee has determined that ~0~ tree species have bean included Sign either Weeding or ~sd.n~ prams {see Appends A). Nearly 500 potentially use tree species can be classified using Me ILCN gu~ide~Ones ase~ndengered ei~tberin ~hol~e or at least in significant po~rbonso~f their range (see Appendix B). Ne~i~the~rlistis comprehensive/ but both a~ suf~c~ntly inclusive ~ allots a ge~ne=~I~assessment. The greatestcon- se~rvat~ion ems are focused on ~erthan.140 tree species ofind~strial fo~es~try value. Oft~bose, slightly more than half areinclud.ed onlvin seedco~llections~nds'whichina)~ono~icbreeding~ter~sareequivient to large, m.ass-select~ion populations. One am ut60sped~sa~ i~dudedin sufBd~n~yin~n~ve beed~g program ms dhatex Mu conservation measures such es seed orchards or included in test or obse~a6.on stands of one type or another, but only a ~ am included in inerna~tio~nal cooperation programs under sow . a..

94 / Forest Trees designation other than as a stand that may be harvested. They are the Eucalyptus in the projects of the Commonwealth Scientific and Industrial Research Organization, the arid-zone and Sahel projects of the FAO, the tropical pine projects of the Oxford Forestry Institute and the Danish Forest Seed Center, the tropical timber species in projects of the Centre Technique Forestier Tropical, and the legumes of the Nitrogen Fixing Tree Association. These organizations and their programs are discussed in Chapter 5. In all of the ex situ programs, the only storage programs other than those included in test or commercial stands are seed and clone banks that mainly serve short-term seed distribution or medium- term storage needs. In situ gene conservation projects of the FAO include 57 species (in at least one stand), some of which are included in conservation efforts concerning 81 species listed as endangered by the FAO (Food and Agriculture Organization, 1986~. For 27 of those 81 species, however, there are no conservation programs for any part of the species, and all have at least some local varieties that are threatened. The biosphere reserve project of the Man and the Biosphere Program at the United Nations Educational, Scientific, and Cultural Organization may ulti- mately provide some support for in situ gene conservation, but at this time species lists do not exist for two-thirds of the 266 reserves in the program, and most of the lists that are available are for species located in regions where they may not usefully contribute to gene conservation. Many endangered but potentially useful species must be considered to remain largely outside the reserve areas. Some of the endangered species are included in national parks, but most are not in protected reserves, and hence, in situ conservation programs that are genetically effective are primarily of the managed resource area type. Of the available techniques for tree genetic conservation, heavy reliance is being placed, by default, on managing ex situ and in situ tree stands. Long-term programs for storage of any other materials are very limited. As long as active interest continues, such stand manage- ment might continue, but there are obvious systemwide vulnerabilities to even temporary lapses in funding or control. For genetic conservation in support of intensive breeding efforts with industrial or agroforestry crops, a broad base of different populations is required to accommodate a variety of performance characteristics and a temporally and spatially varying environment. Many of the 60 or so species under some degree of intensive breeding are currently limited to a very narrow genetic base, and their future breeding can be expected to require expanded base populations. Even such widely used species as Eucalyptus camaldulensis (river red gum) and Pinus patula are already in this state. in,

0~ ~ Off /~ Game R~ / ~ lit is su~ds~ that tam are ago lon~rm ~~rlasm storms ~ ~ e ~ - ~ ~ - ~ - - ~ ~ ~ ~ Foray (i.e ~ savage of ~ to :1~ vearsT far an~v of the bi~-v~lue ~ _ , ~ ~ . am. ~ ~ ~ ~ species. Longing ~n~se~tion ~q~~s~plans ~r-period~ic re~ene~tion of stows and the d~lopmen~t of the longest possible Bade ~ Age to .. .. ~ . . ~ , ~ . .. ^ .. .^.. ^ ... ^ . ., ^ .. .. ~ avow re~enera~on p~~ole~ms~ne~nce fine ~:eres:1n c~yo~mc~s~:or~1n ~ it. ~_~^ be supposed by stable b~gga~nizat~naIstructures; ~a~an~teed~asappro~ pdate by b~ateralin-erna.tionaI cooper action and perhaps cording by aninternationa~Io~g~nizabon. )~aiEorreliance~is placed by foresters on~un~np~roved stands off gild and~slight} improved pop~labo~ns for use and co~nser~a~on. The ex~n~io~n of implant locaIfonnsofT>~#~ s~pc(~nut~treesof the ~estetn~Paci~Ec)~d /~d) ~77bfL~rabic gulp heeJand.~tbeindusion off> Course use ~ ~ eJes~such as three ~ {monkey guzzled ~ ~ , species and sevens spades' on the endangered list~indicae that cu~n~te~ffo~sare~notyestsufRc~nt even for the~s~pedesotrecogn~ably high value. CON TTe chops cf Loch sped es~to conserve and tie m ^ oafs to be employed fire di~atedlargely by either the developme!ntof~high~va1u~e species far breeding~or~ecosys~> con!ervabon. ~ - ~ spe~esotondy potentlalvalue ~rtor~lt~use~ecosyste~n val~es~lirgely men~totgeneLcresourcesib o~the~rtha~nin~nsWe breeding~p~o~r~ms. \4inv species are being harvested con~ne~daUv,~but~thev are not , ~ ~ ,, ~ . . hi, ., maimed in e~n-a~ed plantains anal Hence, are not 1ncluUec an flag p ms In -- an ~- =~ ~ ^ economic utai^. The nut r o~fspedes that are ofsufOdent promise for use in the near fugue to Justly some breeding type of genes rnanagementcou~ld easily be brick the currant nu~aber. Saab develop Lament for use should be talcked by genetic co~nservati~onin whim both in situ end ex situ conservation pro~rar~sincIudesa~mple~sofpopEuJabons ~ a. nom Averse sources. For other species otpotentiaIvalue/o~nl~ya ~ ~ hundred ae~induded ~ at last one test plankton and only a large ~ are included in extensive inte~atio~na~1 Pals. Cost of these are either [~-f~s or Boar species/ are from limited samples that are not represen~dve of the cun~nibabi~tvadabon,and are d~tdb~dio only a ~ ~ pining sites. Thus, it is misleading tp suggest from the information in Appends A that even those s~peciesIis~d are either ensampled or Eli tested. In ~ct/fe~ert~han Reincluded in tee ~stcatego~y . Appendix A are

96 / Forest Trees both well sampled and well distributed. About 200 species of clear potential value should be but are not now included in a designed test, and many more should be managed in multiple conservation stands for observation and testing for possibly intensive use. Unless populations of these species are included in an in situ conservation program, they are immediately vulnerable to at least population-level extinction. The 40 or so species currently included in in situ conservation stands represent a small fraction of potentially useful species, only some of which are under any recognized testing program. For species of even less obvious immediate value to industry or agroforestry, or of little direct use in other forms of forestry, total reliance is placed on natural systems that can withstand human impact. An unknown number are hopefully well conserved with sufficient genetic reserves in ex situ gene banks, designated parks, or other reserves. There is no genetic targeting strategy for forest trees in these programs and, hence, no effort to include useful genetic variation within any forest tree species. Even in agroforestry the flow of materials from initial observations through testing and breeding is not coordinated and there is no research on breeding methods to make otherwise "primitive" or new varieties useful for production systems. The need to activate a coordinated and forceful new level of effort to conserve and manage forestry genetic resources is critical. It seems obvious that a mixture of the above- described approaches could be efficiently organized by an international agency and that this should be vigorously promoted immediately in order to capture and maximize the future benefit from the remaining diversity of tree genetic resources. RECOMMENDATIONS In the areas of conservation and management, additional and increased efforts are needed. Increase of In Situ and Ex Situ Programs In situ and ex situ programs to conserve, manage, and useforest tree resources must be significantly expanded to encompass at least a tenfold increase in the species that are included. Genetic variation is not well conserved for most species, and efforts to conserve and manage tree genetic resources do not encompass global needs. Deficiencies exist both in information and in the extent of activities. For example, ecogeographic surveys must be conducted to

C~s~f2~f ~ Tab Goof? Rso~ ~ /9? assess the need far mana~e~en~tinterve~ntions For many species of coned ootenLa~lva~l.ue new efforts age needed for ex sib~conse~ .. . . . . Ha- ~ - ~ nation. Thdu~=nds of species of yet unknown value mill requ~i~ Sign situ co~nse~rvabon.l~nbop~icalandsubhopica!lregions,~he~ species diversity is Latest, many m~orespeci~ess~hou~ld beconservedin situ. Glot~1 D ~ Base {~3 h~ Id ~ ~ Dew/ I ~ ~ en ad.. , ~ ) ~fi~o~s<y If. If I amp Ifs ~ Ifs rf/~if/~/ ~ A, fief sf~)s/ ~) fifty, cuff As few. Edify Off fig . ~ ~ . Assess ~ at ofthe adequacy of expand effort to Conserve sag des ansd their Renew diversity requires access to u~sefu~1 i~n~fo~rma~hon. A globaldata base would a~ssistin e!f~rtstoidenti~ deOc~nciesi~n global activi~tiesand ~ allocate omen ~a~e~ndin~re!sources 7~l:~!f~. /~ ~ Age If IS Sag ~ Act, fez \,f~yk~Z~)s~>f,~Ss~. lassie ~anaGementplans~mustconside~rthenumber,size~andextent of unsexes needed. They mast be large enough to ensure survival of the ~pulabons and ~ con~re then Chic s~c#= and thev must , , preservetheindepende~nt~eneticdevelopme~nt~o~fseparatepop~ula.tions. ASH - ~ En ^ saw? ~ #~ ~ ~ ~) oaf ~ ~2 ~ >~& ma, ~ If ~ ~Z~~^ ~~' ~ ~ Am. Of ~< OF ~ fog \, fan ~ If Of ~, am, ~T fasts c~/ as ~ Of ~ {~ aft ~e, Us . (... Ex situ~methodsinclude managed stands, and the maintenance of seed, pollen/tissuccultures,orother proportion mat~e:ha~l.s.blanaged sands pe~nitthe Lady avaLabEity ofseed or ~eesand ados studies ofper~r~ance underdif~rentenv-ironments.T~h~eycou~l~d~lin~k conser- vation activities ~itheffo~rtsto deve~)opandimprovetreesby providing accessto ~gniRcantporbons ofthe gene pool Bra paricularspeciesP Ems ~= ~# gaff fo easer Z~-f~ so Fief ~) Of fain Raps ~) /~ r~ oafs fin Of ,~z~ Dallas.

98 / Forest Trees Technologies for storing the seeds of many tree species are available and used. However, the long time that may be needed for growing trees to produce seeds and the potential of environmental loss during a lengthy regeneration cycle can make seed production an expensive and uncertain process. Many species do not survive under conditions of long-term seed storage. For them, tissue culture or cryogenic storage could enable long-term storage. Programs for long-term storage of seed, pollen, or tissues are important adjuncts to managed stands, which can be vulnerable to lapses in funding and control, or to environmentally caused loss. Education and Training Education and training of professionals and technicians in forest genetic resource conservation should be expanded to provide sufficient technical and support staff to meet urgent needs that will result from increased activity. Greater efforts to conserve and develop trees will require a concomitant increase in trained professionals and technical staff. Many of the programs described in Chapter 5 include training activities. However, they cannot meet the needs generated by expanded national and international efforts.

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News reports concerning decline of the world's forests are becoming sadly familiar. Most losses are measured in square kilometers, but a more profound loss cannot be measured. As forests disappear, so do their genetic resources. The genes they possess can no longer aid in their adaptation to a changing environment, nor can they be used to develop improved varieties or products.

This book assesses the status of the world's tree genetic resources and management efforts. Strategies for meeting future needs and alternatives to harvesting natural forests are presented. The book also outlines methods and technologies for management, evaluates activities now under way, and makes specific recommendations for a global strategy for forest management.

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