Forest Trees (1991) / Chapter Skim
Currently Skimming:
4 Conservation and Management of Tree Genetic Resources
4 Conservation and Management of Tree Genetic Resources
Pages 73-98
The Chapter Skim interface presents what we've algorithmically identified as the most significant single chunk of text within every page in the chapter.
Select key terms on the right to highlight them within pages of the chapter.
From page 73... ...
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.
|
From page 74... ...
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
|
From page 75... ...
For most of these species, no direct management interventions are feasible, but some forms of forest management (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.
|
From page 76... ...
However, population densities of large trees, which constitute the most important forest genetic resources, in tropical lowland wet forests are extremely low. In a tropical lowland wet forest in Panama, for example, Hubbell and Foster (1986)
|
From page 77... ...
The promotion 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.
|
From page 78... ...
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
|
From page 79... ...
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.
|
From page 80... ...
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.
|
From page 81... ...
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.
|
From page 82... ...
Such systems can integrate multiple levels of genetic variation between and within usage zones and could provide unique opportunities for experimental genetic management.
|
From page 83... ...
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 overwhelming majority of forest trees are dispersed by a wide variety of animals.
|
From page 84... ...
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.
|
From page 85... ...
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
|
From page 86... ...
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.
|
From page 87... ...
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.
|
From page 88... ...
~ / Off ~ Biotechnology provides also far ma! na~ing Mast Me resources: For example, ene5~call~y ~nifo~ plants can ~ Ted in test babes.
|
From page 89... ...
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)
|
From page 90... ...
... ~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.
|
From page 91... ...
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.
|
From page 92... ...
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.
|
From page 93... ...
The greatestconse~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)
|
From page 94... ...
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.
|
From page 95... ...
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.
|
From page 96... ...
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.
|
From page 97... ...
opandimprovetreesby providing accessto ~gniRcantporbons ofthe gene pool Bra paricularspeciesP Ems ~= ~# gaff fo easer Z~-f~ so Fief ~) Of fain Raps ~)
|
From page 98... ...
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.
|
Key Terms
This material may be derived from roughly machine-read images, and so is provided only to facilitate research.
More
information on Chapter Skim is available.