SEED COLLECTION
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The importance of provenance
‘Provenance, with reference to clonal or seed material, is the geographical area and environment in which parent trees grew and within which their genetic constitution has been developed through artificial and/or natural selection. Although this purely forestry term has no place in the formal taxonomic hierachy, it may, for natural, indigenous forest, and depending on the nature of the populations under consideration and the size and distinctness of their geographical area or ecology, be equivalent to an ecotype, a geographical race, a variety or perhaps more frequently to part of a cline’ (Burley and Wood 1976).
In forestry, the practical and economic importance of matching species and provenance with site and end use has been convincingly demonstrated through a number of internationally co-ordinated species and provenance trials (Palmberg 1980, 1981). The longest-running trials testing a range of Eucalyptus camaldulensis provenances on a wide range of sites showed that the gains in productivity which can be achieved simply by selecting the best-adapted provenances for prevailing environmental conditions may amount to several hundred percent. |
While there have been few systematic studies of geographic variation in acacia species, the available evidence, suggests that substantial intra-specific variation exists. Plans for afforestation with acacias, therefore, should be preceded by taxonomic and genecological exploration followed by systematic sampling throughout the area of natural distribution and evaluation in field trials established over a range of potential planting sites. These trials will indicate the existence and nature of interactions between species, provenance and site and should lead to the efficient utilization of available genetic resources. The choice of provenance may make the difference between a successful plantation and total failure.
The ease with which the boundaries of provenances of an acacia species may be defined depends on the distribution pattern of the species in question. If a species is restricted to small discrete sites, the term ‘provenance’ may be synonymous with ‘site’ and can be reliably applied. The problem of delineating provenances is much more difficult when species occur over extensive areas having fairly uniform ecological conditions. A. aneura, for example, grows widely over the inland plains of Australia. In such a case any provenance boundaries are quite arbitrary.
Special problems associated with the collection of seed to represent provenances of acacias include hybridization and uncertainties in identifying closely related species. Hybrids may be hard to detect in the field and it is therefore essential for later verification that seed of individual trees should be kept separate and that herbarium voucher specimens should be taken from each tree.
It is essential to record the place of origin of all material (seeds, herbarium voucher specimens, photographs and other data) as this forms the basis of provenance research and future action.
Forward planning
Once the broad objectives of the collection programme have been defined, it is essential that ample time be allowed to plan an efficient and practical collection strategy. Comprehensive collections for research will almost certainly require more detailed planning than routine bulk collections and may require a lead time of from one to several years depending on circumstances.
An example of the inputs and time required to plan a major collection can be seen in the FAO/IBPGR Forestry Project (FAO 1980). After three years, the way is now almost clear for the majority of first-stage collections to proceed.
For scientific collections the extent of funding for a particular programme and the availability of experienced personnel will be primary considerations and will dictate what can be achieved in the time allowed. The following steps are usual during forward planning.
Survey of information on species
A literature search may provide information on the natural distribution of a species, its habit, ecology, genetic variability and on fruiting and flowering times in different parts of its range. A visit to Regional Herbaria to examine relevant herbarium specimens may add significantly to the published information on species distributions, variability and reproductive phenology. Personal contact with botanists, field foresters and others who are actively studying or utilizing a species can be rewarding in building up an overall picture of the species of interest.
If the collections are wide-ranging and cross political boundaries, official contacts with the forest services in the states or countries concerned may be essential at an early stage to develop a good working relationship of mutual benefit to all parties. Such action will usually be welcomed by the local forest service if it is assured of free access to information gathered at this and later stages of exploration and seed collection (Burley and Wood 1976). Concerning the FAO/IBPGR Forestry Project specificially, official contacts have already been made in the countries collaborating in the project (FAO 1980) and pertinent information is being provided through a series of handbooks of which this is one.
When all available information is to hand, it should be collated and summarised. Data on natural occurrence is best plotted on maps detailed enough to show the main communications systems (e.g. roads, rivers, railways and airstrips), topography and other data that may assist in the selection of collection sites.
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