Human impacts on forest genetic resources in the temperate zone:: an updated review

Forest genetic resources are considered here in a global perspective, including both cultivated and wild populations. Human interference on global genetic resources results from the impact of different activities: (i) breeding and selection, (ii) seed transfer, (iii) plant population management activities, (iv) alteration of the environment. Expected genetic consequences of these activities were reviewed and revised according to the recent literature. Research on domestication in crop plants reveals that drastic selection can still retain a significant level of genetic diversity including diversity of some genes involved in the selected traits. More important than the impact of breeding and selection in trees, the impact of seed transfer on the whole resource is complex, depending on the origin and genetic diversity of the transplanted material, as well as on the environmental conditions and genetic diversity of the local population in the destination site. Among silvicultural practices, the regeneration phase has a great potential for reducing genetic diversity, but various regeneration practices may result in high genetic diversity. Other treatments, like thinning, may also interfere with the demographic parameters which shape genotic diversity. Thus, different silvicultural systems will have different impacts on the genetic resources of target species but no simple ranking can be made in that respect. Attention should also be given to the genetic resources of non-target species which may be severely affected. Finally, a major impact is suspected from modifications in the biotic and abiotic environment: this should be further investigated. Monitoring the genetic resources globally requires the development of criteria and indicators: some, recent research orientations serving this objective were listed. (C) 2004 Elsevier B.V. All rights reserved.