Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter.
Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.
Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.
OCR for page 73
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
OCR for page 74
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
OCR for page 75
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.
OCR for page 76
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.
OCR for page 77
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
OCR for page 78
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
OCR for page 79
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
OCR for page 80
OCR for page 82
OCR for page 83
OCR for page 88
OCR for page 90
OCR for page 91
OCR for page 92
OCR for page 93
OCR for page 94
OCR for page 95
OCR for page 96
OCR for page 97
OCR for page 98
Representative terms from entire chapter:
situ conservation
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
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
~ / 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
~
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
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.
