Glossary Forest Genetics and Tree Improvement

Adaptation: A change on the part of an individual or population in respect of their environments resulting in better survival, growth or reproduction. This may occur by natural selection, as individuals with favourable genetic traits breed more prolifically than those lacking these traits, or it may involve non-genetic changes such as physiological modification in response to the environment.

Adapted material: Material resulting from natural evolution, or breeding and testing, that is capable of adequate growth and reproduction in a given habitat and that will not have adverse impacts on the health, functioning and productivity of the ecosystem.

Afforestation: The establishment of a forest or stand of trees in an area where the preceding vegetation or land use was not forest.

Allele: An alternate form of a gene, differing in DNA sequence and affecting the functioning of a single gene product (RNA and/or protein).

Base population: The population of trees from which individuals are chosen to establish the breeding population for a tree improvement program. Generally refers to a wild population within a breeding region.

Biodiversity: The variety and variability among living organisms and the ecosystems of which they are part. Biodiversity has three levels or components – ecosystem diversity, species diversity and genetic diversity.

Biogeography: The study of the distribution of organisms over the earth and of the principles that govern their distribution.

Breeding: The science and art of changing the genetic constitution of a population of plants or animals.

Breeding population: A set of trees within which crosses are made to generate material for the next cycle of selection

Breeding region: A geographic area, defined mainly by adaptation criteria, for which improved materials are selected, bred, tested, multiplied and deployed in reforestation.

Breeding value: The genetic value of an individual for a given trait, based on the mean performance of its offspring or other relatives determined through field or laboratory testing.

Clinal or Clinal Variation: A continuous character gradient, usually assumed to be genetically controlled, linked with geography and environment. Adjacent populations merge into one another with regard to character expression with no sharp breaks.

Clone: An individual or group of individuals reproduced asexually from a single organism, and therefore genetically identical to the parent.

Collections, public land: Genetic material gathered and removed from public land for the purposes of reforestation, breeding or research

Community: A group of ecologically related populations of various species that occur in a particular geographic area at a particular time.

Controlled parentage program: A stock production program that includes in its population a number of selected individuals. Production of deployment stock for the program occurs in a production facility (such as a seed orchard or stoolbed) where parents are propagated vegetatively or sexually.

Deployment: Establishment of a new forest through artificial regeneration – planting or seeding designed to meet resource management objectives or obligations. Afforestation, reclamation and reforestation are examples of deployment.

Deployment zone: A geographic area, defined mainly by adaptation criteria, for which tree improvement materials are produced. Deployment zones include breeding regions.

Dioecious: A tree species having female and male sex organs on different plants.

Ecosystem: A complex interacting system that includes all plants, animals, and their environment within a particular area.

Effective Population Size: The average number of individuals in a population that contribute genes to the succeeding generations.

Ecotype or Ecotypic Variation: A genetically differentiated population distinguished from adjacent populations by sharp discontinuities in character expression. Ecotypic variation is a result of adaptive selection. Ecotypes may be geographic, climatic, elevational, or edaphic.

Embryo: That portion of the seed resulting from union of male and female gametes and developing into a mature plant.

Endangered: A term that applies to taxa (population, subspecies, species) in danger of extinction and for which survival is unlikely if the causal factors of loss continue.

Edge Effects: Effects created by the fact that trees near the edge of a stand have more light and less competition and often grow bigger, faster than trees in the interior of the forest. They can also be more susceptible to wind damage.

Endemic: Species or population(s) native to a small region and found nowhere else.

Ex Situ: A method of conservation in which components of biodiversity are conserved outside of the site, away from the natural habitat.

Exotic: An introduced species or population not native to Alberta.

Fitness: The relative ability of organisms of a particular genotype to survive and produce offspring, or the contribution of one of a pair of alleles to the general vigour of an organism.

Gamete: A male or female reproductive cell capable of uniting in the process of fertilization with one of the opposite sex to develop into an embryo.

Gene Flow: The movement of genes (i.e alleles) within a population or between interbreeding populations as a result of outcrossing and natural selection or seed migration.

Gene Pool: The totality of genes and their alleles within an interbreeding population.

Genecology: The study of the genetics of the populations of plants in relation to the ecological niches they occupy; the study of adaptive properties of the populations in relation to their environments.

Genetic diversity: In a group such as a population or species, the possession of a variety of genetic traits that frequently result in differing expressions in different individuals. The variation of genes within a species, the material upon which the agents of evolution act. Loss of variation may prevent adaptive change in populations of a species and reduce its ecological fitness

Genetic Drift: Change in gene frequencies from generation to generation due to sampling errors that operate when an offspring generation is formed by random union of gametes in a finite population.

Genetic gain: The average heritable change attributable to selection in a given trait, from one generation to the next.

Genetically modified organism (GMO): An organism that, through human intervention in a laboratory, has had its genome, or genetic code, deliberately altered through the insertion of a specific identified sequence of genetic coding material (generally DNA) that has been either manufactured or physically excised from the genome of another organism. Genetic modification may be used to alter any of a wide range of traits, including insect and disease resistance, herbicide tolerance, tissue composition and growth rate.

Genetic Variation: Differences displayed by individuals within a species which may be favoured or eliminated by natural or artificial selection. In sexual reproduction, reshuffling of genes through recombination in each generation ensures the maintenance of variation. The ultimate source of variation is mutation which produces fresh genetic material.

Geographic Variation: Variation among individuals and populations found in a tree species natural geographic range. The amount and nature of variation may vary with the species, the extent of its geographic distribution and ecological and climatic diversity of habitats that it occupies in its natural range. A large part of this variation may be genetic and may be further divided into clinal, ecotypic and unexplained classes.

Genotype: The genetic composition of an individual or group that may be either expressed or unexpressed, depending upon environmental effects of a given location.

Germ-plasm collection: A collection of many different varieties, species, or subspecies representing a diverse collection of genotypes and, hence, genetic diversity.

Green Area: The Green Area in Alberta consists of public land that is primarily forested, and is managed for timber production, oil/gas development, watershed, wildlife and fisheries, recreation and other uses.

Habitat: The natural environment in which an organism or population lives. Habitat may refer to all of the organisms and their physical environment in a particular place.

Heritability: An attribute of a quantitative trait in a population that expresses how much of the total phenotypic variation is due to genetic variation.

Heterozygosity: The condition of having one or more pairs of dissimilar alleles.

Hybridization: The processes of cross-mating individuals or populations that possess different genetic makeups.

In Situ: A method of gene conservation where genetic resources are conserved on site, within the natural habitat.

Inbreeding: The intentional or unintentional breeding or crossing of individuals that are more closely related than their parents.

Intellectual property rights: The rights to intangible property that is the product of the human intellect. Intellectual property may be protected by copyright, trademark or patent. The holder of intellectual property rights is usually the person or persons who developed the product or the organization that funded it.

Introgression or Introgressive Hybridization: The incorporation of genes of one species into the gene pool of another. If the ranges of the two species overlap and fertile hybrids are produced, they tend to backcross with the more abundant species. This process results in a population of individuals most of whom resemble the more abundant parents but who possess also some characters of the other parent species.

Lignin: A major non-carbohydrate constituent of wood. It binds to cellulose fibres and strengthens and hardens cell walls. (

Minimum Viable Population: The size below which a population can not remain stable or increase in number, but will decline and disappear, due either to insufficient reproduction or the genetic consequences of inbreeding.

Monoecious: A tree species having female and male sexual organs on the same plant.

Mutation: The process by which a gene undergoes a structural change; a modified gene resulting from mutation.

Natural range: Range of natural distribution of a taxon, excluding any portion that is the result of introduction to a region.

Natural Region: A geographic area in Alberta delineated as part of an ecological site classification and possessing a distinctive combination of physical features (climate, geology, soils, hydrology) and biological features (plant and animal species, vegetation communities). Alberta is subdivided into six Natural Regions which are: Canadian Shield Natural Region, Boreal Forest Natural Region, Rocky Mountain Natural Region, Foothills Natural Region, Grassland Natural Region and Parkland Natural Region)

Natural Selection: The process by which the genetic makeup of a population changes under natural conditions, without human interference, on the basis of its ability to become better adapted, survive or reproduce in a particular set of environmental conditions.

Natural Subregion: A subdivision of Natural Region based on biogeoclimatic factors. The six Natural Regions in Alberta are divided into 20 Natural Subregions.

Pedigree: A record of parentage, sometimes also including data on the performance of parents and other relatives.

Phenology: The study of timing of periodic phenomena such as flowering, growth initiation, growth cessation, etc. especially as related to seasonal changes in temperature, photoperiod, etc.

Phenotype: The sum total of the environmental and genetic (hereditary) influences on a tree; the visible characteristics of a plant.

Propagule: A live entity capable of producing a new mature individual (e.g., a cutting, graft, tissue culture explant)

Population: A group of individuals of the same species that occupy a particular geographic area or region. In general, individuals within a population interbreed and exchange genes with each other.

Provenance: The original geographic source of seed or other propagules. Also, the test population resulting from seed collected from a particular location.

Public land: Alberta “public lands” as defined in the Public Lands Act. Includes Green Area (land managed primarily as forest land) and White Area (land managed primarily for agriculture and uses other than forestry).

Ramet: An individual that has been vegetatively reproduced from the original plant, or ortet, and is thus genetically identical to it.

Rare: A tree species with limited natural distribution in Alberta and which is characterized by small population sizes and/or numbers.

Reclamation: A planned series of activities designed to recreate the biophysical capacity of an ecosystem

Reforestation: The reestablishment of trees on denuded forest land by natural or artificial means such as planting and seeding.

Registration: The process that allows a seed or vegetative lot to be used for deployment within its deployment zone or seed zone on public land.

Rotation: The period of time over which a group of trees matures from first growth to ideal harvestable size.

Rotation Age: The age or time at which a group of trees is ready for harvest.

Seed orchard: A stand of trees, usually several hundred to several thousand in number, established and managed primarily for early and abundant production of seed for deployment. Trees in the orchard are derived and propagated from selected parent trees by grafting or by seed.

Seed zone: A geographic area, defined on the basis of ecological characteristics and genetic information, within which seeds may be collected and freely deployed without any significant loss of adaptation and growth potential. Alberta (excluding National Parks) is divided into 84 seed zones of which 74 are in the Green Zone area. Seed Zones are subdivisions of natural subregions.

Self-Thinning: The process by which the number of trees in a given area is reduced through their own natural competition processes.

Stoolbed: An aggregation of closely spaced stumps, or stools, managed for the production of one-year-old vegetative sprouts (whips). Harvested whips are used for operational planting stock and can be pre-rooted prior to deployment.

Test or Field Trial: A research planting established in a scientific design to develop knowledge or information on the performance of genetic materials (species, provenances, seed sources or progeny) on traits or attributes (survival, growth, pest susceptibility, frost hardiness, wood quality, etc.) of interest.

Threatened: The term refers to taxa for which the potential for loss exists but for which there is insufficient data to determine whether they are endangered.

Taxon (plural taxa): The general term for a taxonomic group, no matter its rank.

Taxonomy: The study of classification of living things. Classically taxonomy is concerned with description, naming, and classification on the basis of morphology. More recently taxonomists have been concerned with the analyses of patterns of variation in order to discover how they evolved and with the determination by experiment of the genetic interrelationships between them.

Viable Population: A population, which maintains its genetic diversity, maintains its potential for evolutionary adaptation and is at minimal risk of extinction from demographic fluctuations, environmental variations and potential catastrophe, including over-use.

White Area: Private and public land in the settled portion of the province, managed primarily for agriculture use, but not excluding other uses such as timber, oil/gas development, recreation, soil and water conservation, and fish and wildlife habitat.

Wild population: A population within its natural range in which the individuals are the result of natural reproduction.

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