Tree genetics: The foundation of forests, past, present and future

Trees have genes? Why do they matter?

Establishing the right trees in the right places is essential to successful forest regeneration, health, growth, and survival. In this context, the ‘right’ tree is genetically suited to the current and future site conditions where it is established. Foresters are acutely aware that management decisions around tree establishment made in the past and present have long-term implications for the services and products that trees provide in future decades or centuries. Healthy, productive trees are the foundation of ecosystem services, socioeconomic benefits including amenity value, and a sustainable, profitable timber yield. Foresters in both rural and urban environments therefore need to choose the best genetic stock, but how do they select the right tree?

In this post, my objective is to give a brief overview of the genetic variation of forest trees, outline how ‘traditional’ foresters working in rural environments utilize this genetic variation, and finally to introduce the challenges of managing the genetic variation of trees in urban forests.


What is genetic variation?

All organisms have a genetic ‘barcode’ contained in their DNA. Variation within DNA causes consistent physical and physiological genetic differences in traits among species, populations within species, and individuals within populations. In the absence of genetic variation there would be no evolutionary basis for differences in survival and reproduction among individuals in response to natural selection. Life as we know it would probably not have progressed much beyond the unappealing, muddy, mineral-rich primordial soup that life emerged from approximately 4.25 billion years ago.


Genetic variation in forest trees:

Obvious genetic differences exist among tree species, and within each species, subtle yet very important differences exist among populations that have become adapted to their local landscapes over thousands of years. Local adaptation is necessary for many widespread temperate tree species because they have geographic ranges that span hundreds or thousands of kilometers across climatically different regions or localities. Large amounts of genetic variation also typically exist among individual trees within any locally adapted population. Genetic variation within populations is the basis for local adaptation of the whole population because some trees are better adapted to their local environment than others. On average, the better adapted trees are likely to grow more rapidly, produce more offspring, and thus transfer their genes to future generations. Therefore, natural selection of suitably adapted individuals leads to long-term genetic adaptation of a whole tree population to the context of local environmental conditions.

Sitka spruce is a fantastic example of local adaptation in a geographically widespread tree species. Large amounts of variation in growth and cold tolerance correspond to genetic differences among populations across its 4000 km species range from California to Alaska. Each local population has become adapted to local environmental conditions over successive generations.


Differences in growth among populations of a single species, Sitka spruce, from south (left; Fort Bragg, California) to north (right; Kodiak Island, Alaska), when grown in a uniform, common garden environment at the University of British Columbia, Vancouver. Photo courtesy of Dr. Sally Aitken, UBC Centre for Forest Conservation Genetics.

Differences in growth among populations of a single species, Sitka spruce, from south (left; Fort Bragg, California) to north (right; Kodiak Island, Alaska), when grown in a uniform, common garden environment at the University of British Columbia, Vancouver. Photo courtesy of Dr. Sally Aitken, UBC Centre for Forest Conservation Genetics.


How do foresters use genetic variation?

Foresters use their understanding of genetic variation among tree species to ensure they establish mixed-species stands that are similar to local natural forests. This is the most coarse-grained level of genetic variation typically used to manage forests. It forms the foundation of ecologically sustainable forest function, including resilience to disturbance events such as drought, fire pests and disease.

Genetic variation among populations within species is important because it means that foresters can choose to replant forest stands by selecting trees from populations within a species range that are adapted to local conditions. These adapted trees are likely to remain healthy, provide ecosystem services and produce timber reliably over their lifetime. This approach is enshrined in the forester’s mantra ‘local is best’. For several hundred years it has been effectively applied in temperate forest regions to manage local adaptation despite little knowledge of quantifiable genetic differences among tree populations became available in the mid-20th Century. The Province of British Columbia natural seed deployment zones are an example of how local adapted populations are operationally defined and maintained (found here). The challenge for this approach to managing forest genetic resources is that climate change disassociates locally adapted populations from the climates they are historically adapted to. It means that trees become stressed, leading to reduce growth and timber production, as well as greater vulnerability to disturbances such as pests, disease and drought. These effects had substantial negative economic and environmental consequences.

Trees naturally colonize new landscapes and adapt to the prevailing climate, but this process takes many generations and occurs far more slowly than rate of climate change some regions of the planet currently experience. Assisted migration and assisted gene flow are techniques that relocate genetic entities (e.g. individuals or populations) to achieve defined population management and conservation objectives. By recognizing and understanding genetic variation among tree populations, foresters have a basis to employ assisted gene flow and assisted migration to mitigate the negative effects of climate change on tree health and productivity. These tools are being used to relocate locally adapted forest tree seedlings to sites within regional landscapes that better match the future distribution of climates they are historically adapted to (further information on assisted migration in forestry can be found here).

Lastly, foresters use natural variation within populations by selecting individual trees that have desirable traits such as growth, wood quality, cold tolerance or disease resistance. This is the finest level of genetic variation used to manage forests. This type of preferential selection and propagation of trees is documented as early as 1664 by John Evelyn in his book Sylva. During the 20th Century, tree breeding programs that select natural variation became recognized as the most effective way to increase timber yields, while managing genetic diversity and trade-offs among other ecologically important traits.


How do urban foresters use genetic variation?

It appears that the management of urban forest genetic resources is far less structured than in traditional forestry, and arguably less resilient to disturbance events or environmental change. Urban landscape planning favors trees that meet aesthetic requirements and the nursery production efficiencies of clonal propagation at the expense of genetic variation. As a result, urban forestry genetic management emphasizes deploying a relatively large diversity of non-native species and cultivated varieties to ensure a diverse and resilient urban forest. This represents the highest level of genetic variation used in traditional forestry. It means proactive management strategies that use genetic variation of locally adapted populations or individuals within species cannot usually be implemented in urban forests to mitigate the effects of future environmental change. An exception may be found in semi-natural or urban parkland areas that emphasize the use of native species and sourced from local populations.

I intend these issues of genetic management in urban forests to be the subject of a series of blog posts. They underlie the need for a new, adaptive genetic management paradigm in urban forestry that is appropriate for the environmental challenges of urban environments and future climates.

Ian MacLachlan

Ecosystem Services: Meanings, origin, and status of the approach in BC Ecosystem Management.

Ecosystems contribute immensely to our quality of life in BC. Imagine our homes, culture, and economy without forest ecosystems to supply wood and wood products, medicinal plants used in First Nations traditions, and clean drinking water for our communities. Or, imagine a landscape without beautiful aesthetics, spiritual inspiration, and cultural heritage, which contribute to our high-quality of life. These, as examples of ecosystem services, are all valid things to recognize and make efforts toward sustaining in natural resources management.

The diverse values for ecosystems can be captured, quantified, and expressed as ‘ecosystem services.’ The ecosystem services approach gained its fame as a means to make a case for conservation by quantifying the value of nature in monetary terms, which led one study’s estimate that the value for Earth’s ecosystems sits around $32 Trillion – a number twice the global GDP. Lately, the approach has advanced significantly as researchers and the broader community come to recognize the breadth of ecosystem services provided by nature, many of which cannot be reduced to a simple dollar value.

The ecosystem services approach has been implemented alongside many tools, frameworks, and applications (see the review here) to improve the efficiency of ecosystem management around the world. For instance, the approach has been adopted as a central framework in nearly all aspects of land management in Europe, mandated by the White House for adoption in all US public policy (including the US Forest Service), and launched internationally through a system of natural capital accounting by the United Nations. So where does Canada stand? Is the term being passed around the water coolers of BC Forestry offices or is yet to migrate this far north?  

The ecosystem services approach is still far from becoming mainstream in BC forest management, but there have long been signs of its arrival. In 2010, the David Suzuki Foundation estimated the value of natural capital in Vancouver’s Lower Mainland at over $5 Billion. Also, Canadian federal research and natural resources institutions have taken up ecosystem services as a research approach and policy tool. For instance, Natural Resources Canada and Statistics Canada have implemented case studies inventorying ecosystem services in Canada’s boreal forests and other ecosystem types across Canada.


Diamond Head Consulting (2017)

Diamond Head Consulting (2017)

In BC’s urban areas, the approach appears to be having having greater on-the-ground influence, especially in municipal planning for urban forestry. For example, many BC municipalities have started to  adopt the ecosystem services approach in their efforts to create livable cities that are resilient to a changing climate. Services like cooling by urban trees, stormwater management, recreation, stress reduction, connection to nature, and so on, are in high demand in cities. In our work with municipalities, we help to identify and measure the ecosystem services that are in demand and promote environmental management alternatives to enhance their supply. Because the approach is practically supported, through applications like i-TREE, scientific literature, Metro Vancouver’s carbon inventory etc., it can be holistically applied to capture the diverse monetary and non-monetary values that residents hold for their urban forests and green spaces. A key strength of the ecosystem services approach from a public policy and planning perspective is that it provides a compelling and relatable platform for communicating planning objectives to the public.

Despite progress in urban areas, I am not aware of the approach being widely adopted in BC’s forest management and planning. That is not to say that ecosystem services are being entirely neglected. Ecosystem services are somewhat synonymous with forest values and forest legislation and regulations do protect multiple values in forests. However, ecosystem services are yet to clearly enter our province’s forest planning or legislative lexicon and the province has sometimes struggled to answer criticism that non-timber values are adequately accounted for and managed. That being said, practice of urban forestry and the ecosystem services approach is increasingly on the radar for BC’s Professional Foresters, so it is likely that the ecosystem services approach will also have a greater influence when it comes time to rethink forest management planning in BC.

Ira Sutherland



This year is looking like a record breaking year for wildfires in BC, with significant wildfire activity increasing all over the province. We have had a long stretch without any significant precipitation across the province, and as such the resources of the Wildfire Service are being stretched thin. With no significant rain predicted in the short-term forecast, this fire activity shows no signs of slowing down.

Across the forests of BC, wildfire is a natural and recurring natural disturbance. Our forests have developed over thousands of years with wildfire acting as a force of renewal, redistributing resources through the ecosystem and creating space for new forests to develop. However, in the last century, wildfires have clashed with other societal values such as safety and economic stability; the threat of wildfire became less acceptable to communities that existed in the forested lands across British Columbia, and wildfire was aggressively suppressed.

This approach of wildfire suppression has led to a highly distorted and problematic forest composition across the landscape: where there once was a mosaic of stands of varying ages and compositions, we have many forests with dense, continuous vegetation and much higher fuel loads. This wildfire suppression approach, when combined with the increased climatic variability associated with climate change, has led to an extremely challenging predicament for forest management in 21st century BC. The forests have a much higher than what is considered natural fuel for wildfire. Fires in these stands will burn with much more intensity and vigor. Where these forests meet human communities, the wildland urban interface, we have the potential for major threats to community safety.


Wildfires are a natural part of the ecosystem, and it is unrealistic to expect to prevent and extinguish all wildfires. Mitigation of the threat of wildfires is key, and allows human communities to coexist with this natural phenomenon. Communities and homeowners should seek advice based on the principles of Firesmart. Sites can be assessed based on the threat the surrounding ecosystem and vegetation pose to wildfire ignition and spread, and a strategy can be implemented and followed for managing this threat. This often includes selective removal of flammable vegetation, reducing vegetation density, and locating structures using advantageous topography to limit wildfire vulnerability.

Wildfire is an integral part of the forests that cover British Columbia, and these forested landscapes have evolved with a dependence on periodic wildfire. However, a balance needs to be struck with the ecological benefits of wildfire and the other values forests generate. We hope communities and homeowners seek advice on how to mitigate the risks of wildfires and safely live in a landscape where wildfire can be expected.

Stay safe out there!

Conor Corbett


Look out for Knotweed !

Japanese knotweed (2-3m tall)

Japanese knotweed (2-3m tall)

It’s early spring and new knotweed is starting to emerge! Knotweed grows very fast - up to 2 cm a day during the growing season and can grow just about anywhere.

Diamond Head Consulting treats and monitors knotweed for numerous municipalities and agencies throughout the Metro Vancouver region. At this time of year we install mow barriers and ‘no mow zone’ signage at known knotweed patches so that mowing contractors don’t accidentally mow the short new shoots. Mowing is one of the main ways knotweed spreads.

Seasonal Identification

The plant’s appearance changes depending on the time of year. In the early spring the new shoots are dark red in colour.

Species Identification

There are four species of knotweed found in our region. Japanese, giant and bohemian all look very similar; height and shape of leaf base are the main differences. Himalayan leaves are lance shaped and narrow in comparison. Japanese and bohemian knotweed are the most common species in our region. Himalayan and giant knotweed are here too but relatively rare.


Knotweed has negative ecological and economic impacts.


  • Displaces naive plant communities. reducing habitat and food sources for wildlife
  • Degrades fish habitat
  • Increases risk of soil erosion and sediment in water courses


  • Permeates concrete/asphalt and building foundations
  • Obstructs sight lines
  • Requires maintenance on trail and road edges
  • Dead stems can clog drainage systems
  • Can cause slope instability in winter
  • May reduce property values
Bohemian (2-5 m tall)

Bohemian (2-5 m tall)

Himalayan (1-1.5m tall)

Himalayan (1-1.5m tall)

Giant (>5m tall)

Giant (>5m tall)

How does Knotweed spread?

  • By seed and plant fragments
  • Hitching a ride on equipment; mowers and vehicles
  • Movement through water courses


If you think you have knotweed on your property clink the link below and know what KNOT to do !


Amy Hendel

Tree Pruning - The Basics

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There can be many objectives when pruning a tree. These include weight reduction to reduce the potential for branch failure; providing clearance to buildings or infrastructure; reducing shade and wind resistance; maintaining health; promoting flower or fruit production; improving a view; or simply improving the aesthetic look of the tree. Regardless of the aim, cutting a tree and removing foliage will expose the tree to bacterial or fungal infection as well as inducing different stress responses depending on the type of tree. Therefore, pruning should be done properly to allow the tree the best chance to heal and maintain it’s health.

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Before making any cuts it is important to have a basic understanding of how branches are attached to each other and to the trunk of the tree. Where a smaller branch sprouts from the parent branch or trunk, there is a branch collar (usually a ridge that runs perpendicular across the base of the smaller branch at about a 40 degree angle (depending on species) the parent branch. It is formed by overlapping wood from the branch and trunk which forms a strong attachment between the two. The physical properties of this area, combined with chemicals produced by the tree make it difficult for infection to spread from the branch into the trunk. For this reason it is important when pruning, to make a clean cut just outside the branch collar. If the cut is made here without tears or breaking, the tree will have the best chance of healing over the cut.

Poor cuts are those made too far from the branch collar, or too flat to the trunk (flush cut). To avoid tearing, make a small cut (1/4 to 1/3) through the underside of the branch a little way out from the collar, then make a second cut on the upper side slightly further out still which overlaps the first. This will enable the branch to snap and separate neatly with splitting or tearing down past the collar. There is a general rule that arborists use when selecting which branches to cut, called the Rule of Thirds. This rule states that where possible the branch being removed should be no more than 1/3 the diameter of the parent branch or stem from which it originates. This rule is here to ensure that the cut is not so big that the tree can’t possibly heal over it, and leaves a strong enough branch or stem to assume what’s called ‘apical dominance’ or in other words become the leading part of the remaining stem.

When cuts are made too far from the collar a stub is left. This stub will die back to the branch collar leaving dead material that the tree takes a long time to grow over and is perfect for bacterial and fungal infection. If this becomes infected there is potential for the infection to spread to the trunk of the tree. Flush cuts, although they may not look like it, actually expose wood tissue from the trunk or stem. This opens up the parent branch or trunk to infection and decay in major parts of the tree can be catastrophic. So remember - find the branch collar and follow just outside it for every cut!

There are three main types of pruning cut; thinning, reduction and heading. Thinning cuts remove selected branches, generally within the crown, to improve light penetration through the crown and increase air flow. Reduction cuts however, remove branches at the exterior of the crown to keep the tree contained. The afore mentioned pruning techniques apply completely to these types of pruning. Heading cuts, on the other hand, require a different technique and for the most part will require more maintenance. Heading cuts are when a branch is cut to a bud or to a lateral branch too small to assume apical dominance. In trees heading cuts stimulate a stress response which causes multiple ‘suckers’ or small straight branches to appear from the nearest buds. These are called epicormic growth and it is basically the tree trying panicking and trying to quickly replace lost foliage. In certain species and situations heading can be a good way to contain a tree while maintaining a full looking crown (known as ‘pollarding’), but care must be taken to select species which respond well to this type of pruning and to keep up the maintenance so the fast growing suckers do not get out of hand.

A common technique many people have heard of is ‘topping’, where the top (apical meristem) of the tree is removed to a predetermined height. Topping used to be commonplace, but as more has been learned about the response of trees to these cuts it has been outlawed in most situations among professional arborists. Topping often leads to branch die back, decay and sucker growth which if left unchecked can produce multiple unstable tops. It can appear to be a cheap way to fix the problem of a tree that is too tall, but the real costs come later when the tree has develops health problems as a result.

If the rule of thirds is followed, the cuts are made carefully and only minimal amounts of foliage are removed, the tree will be left with the greatest chance of healing from it’s surgery and continuing to thrive.

George Keays


Salmon Safe - Urban Site Certification Program

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What is Salmon-Safe?

Salmon-Safe is a third-party certification program that recognizes and rewards responsible, eco-friendly management practices that protect Pacific salmon habitat and enhance water quality on agricultural and urban lands.

Founded in 1997 by the Oregon-based Pacific Rivers Council, Salmon-Safe is a non-profit accreditation program aimed at maintaining and enhancing salmonid habitat in the Pacific Northwest. This market-based mechanism allows landowners and land managers to seek independent endorsement in the form of certification of their management practices, provided they protect water quality and restore habitat. Since the program’s inception, Salmon-Safe has become a leading regional eco-label with more than 95,000 acres of farm and urban lands certified across the Pacific Northwest. The Salmon-Safe retail campaign has been featured in 300 supermarkets and natural food stores, delivering important marketplace benefits to certified suppliers and landowners.

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In 2010, the Pacific Salmon Foundation and Fraser Basin Council began working in partnership with Salmon-Safe U.S. to pilot the program in BC. Since then, it has expanded to vineyards and other specialty crops, certifying more than 10,000 acres of B.C. agricultural land. In 2013, Salmon-Safe B.C. launched Salmon-Safe Communities to recognize and certify urban properties and to promote the protection of Pacific salmon within urban context.

How can an urban building be safe for salmon?

Urban developments, including commercial, industrial and residential activities, can have long-term impacts on fish and other aquatic species, even if they are not directly adjacent to a stream or waterway. In rainy Vancouver, contaminants from vehicle and industrial pollution, metal and concrete surfaces and hazardous and waste materials can accumulate in rainwater and flow through storm drains into rivers and marine habitats. In fact, stormwater runoff from impervious surfaces is the largest non-point source of pollution in urban areas.

Land and property owners can help protect salmon habitat and water quality by preventing runoff from their buildings and parking lots from entering streams and storm drains. To help reduce stormwater runoff, managers can use permeable surfaces like raingardens, vegetation buffers and permeable paving to capture and infiltrate water. Stormwater can also be collected and used as grey-water to reduce dependence on municipal water-sources. Managers can also help promote healthy salmon habitats by restoring impacted streams and waterways, reducing the use of harmful pesticides in landscaped areas, and using drought-resistant native plants to reduce water-use.

How can I help?

If you are interested in helping Salmon-Safe achieve a healthier, cleaner environment for our vital salmon stocks, consider seeking a Salmon-Safe Certification for your farm, business or development. This certification will allow you to join innovative and pioneering companies like Nike, MEC and YVR, and promote your brand as an eco-conscious community member taking extra effort to protect our shared resources. As a consumer, you can choose Salmon-Safe certified brands and learn more about the salmon-safe program at

Theraesa Coyle

Bird Nest Surveys: What to Know Before Removing Trees

Thinking of clearing trees on your property for a new development, to remove dead, dying or damaged stems and limbs, or to create a better view? Whatever the reason, there are a few considerations before you begin. The first is to be aware of your local tree bylaws and other regulations that may apply. A second consideration is the potential for nesting birds. In some municipalities, a tree permit will not be issued prior to conducting a bird nest survey.

Thinking of clearing trees on your property for a new development, to remove dead, dying or damaged stems and limbs, or to create a better view? Whatever the reason, there are a few considerations before you begin. The first is to be aware of your local tree bylaws and other regulations that may apply. A second consideration is the potential for nesting birds. In some municipalities, a tree permit will not be issued prior to conducting a bird nest survey.

Nesting season in Metro Vancouver for most birds occurs between March 1 and August 30, as directed by the BC Ministry of Environment in Develop with Care 2014: Environmental Guidelines for Urban and Rural Land Development in British Columbia. Some birds, such as Bald Eagle and Great Blue Heron, have longer nesting seasons that begin as early as January and last until September. Tree removal during these periods may affect nests and nesting behaviour of some birds. If possible, all tree removal and maintenance activities should occur outside of this period. However, if trees must be cleared during this time, a nest survey should be conducted to meet your legal requirements.

The objective of a nest survey is to determine, to the best possible standard, if any active bird nests are present at the site prior to tree clearing or vegetation removal. This survey can help identify any active or protected nests and establish protective no disturbance buffers prior to commencing work. If active nests are identified, tree clearing may be delayed until fledglings have left the nest or another nest survey has been completed to verify that there are no active nests on site.

Diamond Head Consulting has Qualified Environmental Professionals who have significant experience conducting bird nest surveys in urban and rural areas as part of development. We also complete wildlife management plans and environmental site assessments. If you’re considering clearing trees or removing vegetation during the bird nesting window, please contact a member of our team. We would be happy to help you out.

Stormwater Management

Trees might have a larger stormwater management benefit than previously thought.

We plant and cherish trees in our cities because they provide us with many things we value, from beauty and shade, to stress relief and habitat. While some tree benefits are well studied and understood, others are less known. One tree benefit that has not been fully studied is that of storm water management.  

Trees contribute to stormwater management by reducing runoff, intercepting rainfall, and allowing for more infiltration into the pervious soil. A variety of tools exist to help us estimate the role of trees for stormwater runoff.

Trees contribute to stormwater management by reducing runoff, intercepting rainfall, and allowing for more infiltration into the pervious soil. A variety of tools exist to help us estimate the role of trees for stormwater runoff.

The iTree Hydro tool developed by the USDA Forest Service is available as part of its series of tools to quantify urban forest benefits. It allows users to test the effect of changes in the urban forest on stormwater runoff quantity and quality.

Our research using the tool has highlighted the importance of pervious ground cover to reduce stormwater runoff, as well as the modest but beneficial impact of trees. [More information on this research: link to my master’s project]

Recent research in Metro Vancouver has now shown that the urban forest can intercept a significantly higher proportion of rainfall than observed in natural, forested conditions. With more research measuring tree benefits in the urban context, we will keep improving our understanding of urban forest benefits, and bettering our communities.

Camille Lefrancois