Sustainable Forest Management (SFM) Toolbox

Forest Genetic Resources

This module is intended for managers of forests and conservation areas as well as for silviculturists, restoration ecologists and others involved in conserving and managing tree-based resources or who work with forest planting materials. The module provides information on the conservation and management of forest genetic resources and gives links to other useful materials. 

Forest genetic resources contributes to SDGs:

What are forest genetic resources?

Forest genetic resources are the heritable materials within and among tree species and other woody plants (FAO, 2014a). Forest genetic resources underpin the adaptive potential that has enabled trees to be, in evolutionary terms, among the planet’s most successful types of organism. The practice of genetic conservation is not intended to conserve every genetic variant (or “genotype”) – indeed, this would be impossible because individuals of sexually reproducing species are genetically unique. Rather, the aim is to conserve the evolutionary potential of species, which means ensuring the continuation and functioning of the processes that shape and maintain genetic diversity. Conservation efforts may also focus on conserving particular traits (characteristics) of trees and other woody plants, such as resistance to pests, diseases or drought.

Although genetic resources are often neglected in planning and implementing forest management, their conservation is essential for sustainability. It is critical, therefore, that forest managers understand the point at which ignoring genetic aspects can prevent the achievement of forest management goals.

Why are genetic resources important?

Trees vary – both within and among species – in their growth rates; stem form; seed production; tolerance to pests, drought, heat, salinity and heavy metal toxicity; and many other characteristics. The ability of trees to adapt to environmental changes depends on the level of genetic variability in their “adaptive traits” – characteristics that confer tolerance of, or resistance to, new environmental challenges.

Most tree species have high levels of genetic diversity, presenting great (and largely untapped) potential for improving tree products such as food, fibre, solid wood and forage and increasing the delivery of environmental services (such as water supply regulation and carbon sequestration). Tree selection and breeding programmes attempt to take advantage of genetic variability to improve valuable traits; such programmes have the potential to achieve the same dramatic improvements in forest production that have been made in food crops. The time required to achieve such improvements is longer for trees than for most agricultural crops, however, because of the late initiation of sexual reproduction in trees and their longevity. Evaluating, conserving, testing and using genetic diversity is vital for ensuring the future production of goods and environmental services from trees.

Genetic diversity of forest trees

Genetic diversity of forest trees

Genetic diversity in any species originates as mutations in the genetic code, DNA. Although most mutations are deleterious and are removed rapidly through natural selection, beneficial mutations can confer selective advantages on individuals carrying the variant genes. Thus, the carriers of beneficial genes have higher “fitness” (that is, they are capable of producing more surviving offspring) and are better adapted to their environmental conditions compared with individuals not carrying those genes.

Genetic diversity is maintained by gene flow via pollen and seed movement within and among populations. In general, large populations maintain more genetic diversity than smaller ones; conversely, genetic diversity is restricted by small population size and isolation. Isolation may be the result of distance from other populations of the same species or due to physical barriers preventing the movement of pollinators or the dispersal of seeds across landscapes.

Adaptation to conditions as they vary along environmental gradients maintains genetic diversity among distinct and overlapping tree populations. Understanding patterns of variation in adaptive traits is important in selecting suitable seed sources for planting.

Most tree species are out-crossing, which means that:

  • flowers on one tree are usually pollinated by another tree;
  • they respond poorly to inbreeding (i.e. mating between close relatives); and
  • they have high genetic diversity relative to many other species.

In their natural state, therefore, most tree species have considerable potential for both adaptation to environmental change and genetic improvement in productive traits, thereby increasing their usefulness to people.