Abies alba - Technical guidelines for genetic conservation and use for silver fir

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Since silver fir stands have been regenerated mainly naturally for a long period, there is reason to assume that they have preserved their original genetic structure and diversity, although the genetic composition of silver populations may have been modified by adaptation and/or drift processes. It is evident that in several parts of the distribution area genetic variation has been reduced due to the mentioned decline of silver fir. This reduction of population sizes may have reached a stage where the future survival of locally remnant populations is no longer guaranteed.

To preserve the population-specific genetic structures of silver fir, i.e. locally common alleles and the area-specific allele frequency distribution, many different populations from various distribution areas should be selected systematically for gene conservation purposes. The most effective way to conserve larger occurrences of silver fir and their genetic resources is through in situ conservation of stands and populations as well as their natural regeneration using long-term and small-scale regeneration methods. Additional activities are the promotion of silver fir individuals by tending and thinning, and the strict control of game. If planting of silver fir is required, culling for height of plants in the nursery should be avoided since genetic effects of this procedure cannot be excluded. In case of occurrences with a low number of individuals, enrichment planting in addition to the natural regeneration is recommended with plants from other, larger occurrences of the same region to avoid a higher frequency of half-sib offsprings and subsequent inbreeding in the next regeneration stage.

To avoid risks of interspecific geneflow, reforestation using exotic Abies species in the vicinity of silver fir stands should be strictly monitored. Only in marginal areas, with highly depleted genepools and where ecological conditions are very degraded could interspecific mating help to create new adapted genotypes. In all other cases, it should be avoided.

For small populations with a decreased number of individuals, and in addition to in situ conservation measures, the establishment of ex situ gene conservation seed orchards is highly recommended in order to overcome the isolation of individuals and to promote outcrossing. The sampling of single trees does not affect the genetic structure if a sufficient number of individuals is considered. However, sampling should be done exclusively in indigenous populations, randomly in respect to the phenotype but representatively in respect to ecological variation. Wherever possible, the genotype of the individuals sampled should be assessed and considered, e.g. using gene markers to avoid loss of genetic variation and a reduced diversity.
Complementary to in situ and ex situ conservation measures, seeds of silver fir can be stored in genebanks for about 3 to 5 years provided that outcrossing has taken place among a minimum number of 20 individuals. To overcome the negative effects of isolation in silver fir relicts in the short term, the collection and storage of pollen in combination with artificial pollination of mature trees could be an efficient but expensive approach.

In the European Community, silver fir is under the EU Directive on the marketing of forest reproductive material. For reforestation or re-introduction of silver fir, only forest reproductive materials are to be used according to the regulations and must be suitable for the site conditions in question. In nations not under EU law, the procurement of forest reproductive material should follow the principles of approval, identification and control. In every case, however, recommendations should be developed for the proper use of forest reproductive material.

Journal/Series: EUFORGEN Technical Guidelines for Genetic Conservation and Use
Publication Years: 2003
Publication Format: Folder; PDF
ISBN 10: 92-9043-607-7
ISBN 13: 978-92-9043-607-2
Language: EN
Pages: 6 p.

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