Types of Silvicultural Activities

Silviculture Encompasses Many Activities

There are a large number of different activites commonly practiced in the field of Silviculture. These include, but are not limited to: Brushing, Spacing, Thinning, Silviculture Surveys, Pruning, Planting, Browse Control, Vegetation Management (including Herbiciding/Spraying), Cone Picking, Nursery Services, Fire Fighting, and other related activites. On this page, we'll describe what is involved in each of those activities.

Planting

Tree planting is the type of silvicultural activity that is probably most well-known to the majority of Canadians. Every year, tens of thousands of young workers head to the bush to plant trees as a summer job, an activity which takes place in every Canadian province.

Typically, the main species that are planted are coniferous, especially types of pines and spruce, although several dozen species do get planted in Canada in varying amounts each year.

Since tree planting is such a complex and high-profile part of the field of silviculture, we decided to give it a page of its own on this site. Check out that page to learn more (you'll see the link at the top of this page).

Browse Control

After the seedlings have been planted, one of the risks to their development comes from animals. Certain animals will eat certain species of trees when the trees are still young and haven't become too coarse and woody. Even after these species have been growing for a year or two, the green tops of the trees may still be appealing as food, and since it is the top of the tree where growth is focused, the growth of that tree is considerably set back if an animal chews the top.

Some of the animal species that cause the most problems are deer, elk, moose, and rabbits. Some of the tree species that are most susceptible include the various types of cedars and pines. Broadleaf trees are also more susceptible than coniferous species, although of course there are far fewer deciduous trees planted in Canada than coniferous species.

In a few select locations where the cost of reforestation is very high per seedling, one solution is to employ various browse control methods. A conventional method is to temporarily place browse control cones over the top of the young seedlings. These cones will remain in place for several years. They allow sunlight to filter through to the seedling, and they allow for vertical growth, but they protect the seedling from being eaten until it reaches a height of several feet. Once the seedling has become well established, workers will remove the cones and the tree will have more room to continue its growth. One of the photos at the bottom of this page shows a group of white browse control cones.

Another less conventional method of browse control is through the application of biological agents, such as Plantskydd (which contains ingredients such as pig's blood). An application of such an agent makes the young tree smell or taste bad to the animals, so they won't eat it.

Cones are typically 3-4 feet in height and are staked with cedar stakes that are 3/4 inch thick and 4 to 5 feet long. These stakes are hammered into the ground, most often by the people who are planting the trees. If the cones are not placed almost immediately, the trees may be nibbled away by the following day. In some locations (for example, on Haida Gwaii), deer have been seeing following tree planters to eat all the young seedlings.

Browse control methods are not common in large commercial plantations in areas where costs are consistent with industry averages, and where survival rates are high. It is more common to see browse control attempted in places like the BC coast where the cost per tree can be extremely high compared to industry averages.

Vegetation Management

Vegetation Management encompasses a variety of activities, such as herbiciding (either aerial sprays or targeted applications), targeted manual cutting via methods such as brushing (described in more detail below), indiscriminately clearing large amounts of vegetation through the use of heavy equipment (such as mulchers), and grazing by animals.

The point of applying herbicides is to apply chemicals which will cause mortality in most species, but which will not have a negative effect upon the crop trees that need to be retained. As noted above, the application of herbicides is generally broken down into two methods. Aerial spraying might include very large scale spraying through the use of rotary-winged aircraft (helicopters) or fixed-wing applications (small aircraft such as crop-dusters). On a smaller scale, some herbicide programs rely solely upon manual application methods, where workers traverse through an area wearing backpack sprayers, and manually spray the pesticides across the block. Backpack spraying is slower, but it is generally less expensive and runs less risk of trespasses into no-spray zones such as riparian management areas alongside streams and adjoining bodies of water. With herbicides, naturally, there are a lot of restrictions, and depending on the province, there are varying rules about which ones may be applied, and the exact operational ground rules that come into play.

Targeted applications include processes such as basal bark application, where liquid herbicides are sprayed directly onto the base of trees, shrubs, and shrubby vegetation that need to be eliminated. Basal bark applications are generally performed on non-preferred and non-acceptable species of trees which are competing with the crop trees. The herbicide, in theory, will kill the trees and vegetation to which it is applied. This type of treatment is more effective than aerial applications in areas where the stems being targeted have become too large to be susceptible to a light application of a diluted herbicide.

Brushing

Brushing is an activity which typically takes place a couple years after an area is planted, or a couple years after natural regeneration starts to take hold. At this point in the growth of a stand, the young trees often fight with other plants and brush for critical resources such as water, sunlight, and nutrients. Brushing can also take place immediately after planting on high-growth sites. In some cases, tree planters are required to mark all young cedar seedlings with hi-visibility flagging ribbon so the brushers can work more effectively. Brushing is a way to reduce or eliminate competition for the young trees, as they grow at a far slower rate than many of their competitors.

Brushing is almost always done with a special type of mechnical saw. A brush saw is designed to be able to be used very much like a whipper-snipper for residential grass control, and it is much more effective and safer than a chain saw for eliminating competition from small and light plant growth. A brush saw is also much safer than a chain saw, although it is not usually as effective on woody competition once stems start to get more than a few inches in diameter. However, on a brushing contract, the saw is usually being used to eliminate competition from light brush and vegatation (and to a lesser extent upon competing trees).

Before a successful brushing application, you might look at a young stand and not really be able to see any viable crop trees because of the amount of brush and vegetation. However, after brushing, you will probably suddenly be able to see large numbers of young crop trees, perhaps a few feet each in height. Without all the competition from vegetation, the growth rates of these crop trees will certainly be enhanced.

Here is a good reference link: http://www.for.gov.bc.ca/hfp/publications/00183

Pruning

In general, pruning is a horticultural and silvicultural practice involving the selective removal of parts of a plant, such as branches, buds, or even roots. In the field of silviculture, the typical goal of pruning programs is to force trees into channeling their energy into vertical growth, so the fibre being produced by the tree goes into the height and diameter of the stem, rather than into low-lying branches. Pruning can also be a value-added service, minimizing the prevalance of knots in the lumber that will eventually be harvested from the tree.

Workers will use pruning shears or saws (mechanical or hand-saws) to perform pruning work. Axes and machetes, and any tool that involves impact to the stem, are not effective tools. This is because they cause too much damage and scarring, and do not create a clean cut. A rough cut enhances the chance that undesirable fungi or other organisms will infect the tree. Chain saws are also undesirable, because they are too rough and lead to scarring.

Pruning should not be done during the spring, when bark is loose, as the risk of damage to the stem is greater. The late fall is a good time for pruning, for a variety of factors such as lower risk of infection by biological organisms. The winter is also an excellent time for pruning, when growth is minimal because the tree is dormant. There is also one other major benefit to winter pruning programs: they can provide employment for silvicultural employees at times of the year when other silvicultural activities (such as tree planting) are simply not possible due to snow.

Pruning is also done to control blister rust in white pine. Lower branches are removed and infected bark is excised to prevent the spread of the rust.

Silviculture Surveys

When foresters are trying to understand characteristics such as the success of a plantation, the amount of species diversity, the density of various species, growth patterns, etc., it is not practical to do a complete inventory by counting and measuring every single plant and tree on a block. Instead, statistical samples are taken to give a reasonable estimate of the information being sought. This practice is called surveying. Silviculture surveys should be distinguished from land surveying, which is another field of work that involves measuring property boundaries and a very large number of other related practices.

Timber Cruising is traditionally looked upon as a logging activity, although technically, it is a type of silviculture survey. Timber cruising involves the study of representative samples of a stand of mature timber, to study the quality, heights, diameters, ages, and species diversity. Other external factors also need to be taken into account, such as the access to the area, potential erosion or vegetation management issues, susceptible bird nests and animal lairs, etc. At the end of the assessment, the person doing the timber cruising is able to come up with an assessment of the approximate value of the stand, which can then be useful for activities such as determining real estate transaction prices, fibre sales, and so on. Timber cruising is also useful because it is a great way for foresters to determine the overall health of the forest, and to become better acquainted with the characteristics of a particular stand of trees.

Regen Delay Surveys are used in certain provinces to determine whether or not a harvested area has met its mandated early regeneration requirements. There is usually a specific deadline for a Regen Delay survey, which could be, for example, four years from the date of harvest. By this date, surveyors must assess the success of natural regen combined with planted trees (if any) to determine if the stand meets a passing grade. Regen delays are performed on young plantations, so it is common that the trees being surveyed are quite small. Obviously, these surveys must be done when there is no snow cover, and it is often easier to do them in the early spring, before green-up, or perhaps in the late fall after the leaves drop off the brush. Of course, there is a small advantage to having leaves ON the brush, because it may help the surveyor to identify certain species a bit more easily.

Stocking Surveys are performed fairly frequently, to simply assess the density of viable crop trees on a plantation. This may be more of an "unofficial" survey than other types of survey, but it is useful because it might be performed several times on a single plantation over a period of years, giving foresters an idea of the health and growth rates of the young stand.

Free-To-Grow Surveys are used in certain provinces to determine whether or not a harvested area has met its mandated reforestation requirements. The primary difference between a Regen Delay survey and a Free-To-Grow survey is that if a block or stand has passed the FTG survey, then the logging company becomes legally exempt from any further requirements to bring the land back to productive forest. Free-To-Grow surveys occur much later in the development of the young stand, perhaps twelve to fourteen years after initial harvest. Snow cover again is an issue that restricts the ability to perform a FTG survey, although it is a much lesser concern than for a Regen Delay survey, unless the snow starts to get fairly deep. Because Free-To-Grow surveys are sometimes affected by broad-leaf vegetation that is competing with trees in the stand, it is sometimes necessary to perform these surveys at times of the year when there are a lot of leaves on the brush, to properly assess competition from vegetation.

The above are just a few of the many types of surveys that are performed by Silviculturalists. There are many types of surveys relating to volume of fibre present in an area. Obviously, most survey activities take place in seasons other than winter, but there are other types of work/surveys, such as Pine Beetle Probing (looking for evidence of Mountain Pine Beetle infections) that can take place during the winter months, due to the fact that the stems of mature trees can be examined at heights above the level of snow cover. Doing survey work has an advantage in that there is a much longer employment season than for activities such as tree planting.

Spacing & Thinning

Spacing and juvenile thinning is typically performed on stands with developing trees, using brush saws for stems of up to 4-5 inches in size, and using chain saws for larger wood. Spacing usually doesn't happen until a stand has had several years to start to establish itself properly, once the crop trees are firmly established above the heights of any competing brush. One advantage of Spacing and Thinning compared to some other types of silviculture-related employment is that they can be done throughout most months of the year, save for during very thick snow cover.

During a spacing program, the workers will make assessments as they work through the stand, determining which trees have the most potential for future growth. Several factors are taken into consideration here: preferred vs acceptable species, the height and diameter of trees, proximity to other good crop trees, form, vigour, any evidence of potential disease, etc. Once the worker has determined which are the best trees to keep, depending on the previously mentioned considerations and on density requirements for the stand, all other competing trees will be cut and left on the ground to decompose. This process allows for more space and sunlight for the remaining good trees in the stand, so they will grow faster than they would have before the weaker competition was eliminated.

There is another type of thinning, commercial thinning (described further down this page) in which any cut trees are harvested, but that type of work usually happens in older stands. Spacing and juvenile thinning is appropriate in stands with a variety of ages ranging from perhaps five to twenty years after planting.

Although uncommon, sometimes instead of using brush saws to cut out the unwanted trees, a process called girdling is employed. Girdling happens when workers use curved knives or machetes to strip the bark from a ring around an unwanted tree, and several months later, the tree dies from lack of nutrients. This procedure is employed to kill deciduous species that compete with conifers, typically alder or aspen. The cambium layer (the bark) is completely removed in a thin strip all around the trunk of the tree, denying the tree the ability to feed and so killing it. Girdling is used when falling the tree would create too much damage to existing young conifers. It is also considerably more cost effective. Cutting the tree down would also just encourage growth of new shoots. Special girdling tools are also used sometimes.

Nursery Services

Forest nurseries or tree nurseries are specialized operations that are able to grow large quantities of commercial tree seedlings for large buyers. Most of these nurseries specialize only in the production of certain species of trees, and don't diversify with plants or flowers.

Most forest nursery facilities are able to produce millions of trees each growing season. In fact, the average order at these facilities is usually for hundreds of thousands or even millions of seedlings to each individual customer, and these orders are planned and coordinated more than a year in advance. Seedlings are grown in styrofoam blocks in various mixtures of peat, perlite, vermiculite and some composted materials, sometimes with timed-release fertilizers added. In the styro blocks, different sized cavities and planting densities are employed to produce seedling with smaller or larger plug sizes. The plug itself contains the rootmass of the tree. For rocky planting sites, a smaller plug may be helpful to accommodate shallow soils. In a high yield site, a larger plug (and hence a larger seedling) may be used to try to get an advantage over competing brush. Foresters juggle the extra growing and planting cost for larger seedlings against the benefits of possibly avoiding future brushing treatments. Larger seedlings are also less likely to suffer from the same mortality levels as smaller seedlings.

Forest nurseries typically have two production runs and lifts each year. The first will take place in approximately July, when new stock trays are set up and seeded. These trees grow through August, September, and early October, then from mid-October through the end of November, the trees are "lifted" (pulled out of their growing trays) and then packaged into wax cardboard boxes or other types of storage containers. The trees are then placed into freezers for over-winter storage, and the sub-zero temperatures make the trees go dormant for the winter. When they are pulled out of the freezers in the spring, they need to sit outside for perhaps ten days to thaw out properly, then they are delivered to planters for planting in the spring season, usually April through June. These are called the spring lift trees, or over-wintered trees. From the time they arrive at the planting site until the time that the planters actually start to plant them, the cartons are often stored in closed, refridgerated trailers called "reefers" as the seedlings slowly continue to wake up from their dormancy period.

The other production run will start in the early spring. Again, trees are seeded in March and then grow throughout the spring months, up until the middle of June or even the start of July. At this point, they are lifted and packaged. This is called a "hot lift" because the trees are wide awake and growing at full tilt as they are packaged into their shipping cartons. They are then sent directly to the planting sites, and are planted almost immediately, sometimes less than 48 hours after they are lifted by the nursery. If these trees need to be stored for a few days, they are sometimes stored outside with the boxes open and perhaps covered by a tarp or shade cloth to keep direct sunlight from drying them out. The respiration of the hot-lifted trees produces a bit of heat and humidity, which is another reason why they aren't always stored in trailers, although a good refrigerated trailer is easily able to keep the boxes from overheating for several days.

Cone Picking

Cone picking is not a common job in the silviculture field, and only a very limited number of contractors specialize in doing these projects. Typically, when a project is undertaken, it might only last for a month or two, and the goal is to recover enough seed to last for several years. Seed from some collections, when stored properly, can last for as long as twenty years or more and still remain quite viable. Due to the logistics in setting up a project, it makes sense to harvest fairly large quantities at one time, and store the excess for years until it runs out. The seed is then used by forest nurseries to grow new seedlings. Sometimes, it will be the nursery that buys the seed from the contractor, and at other times, it will be a public or private mill that runs the cone picking operation (or contracts it out) to have seed to give to the nurseries, for their own seedling orders.

There are several variations on cone picking operations. One common method is for a crew to work from a central landing. A helicopter with a high-topper attachment will fly around and cut the top couple metres off a tree that has a lot of cones, and will fly the tree back to the landing. Pickers will then strip the cones by hand and fill buckets, to be given to the contractor in return for pay. This is typically a piece-rate position, so the more buckets you pick, the bigger your paycheque. Pickers will sometimes coat their hands with oils such as margarine to prevent the resins on the cones and trees from sticking to their hands and fingers. It sounds odd, but you don't want your fingers to become all gummed up. The faster you can pick, the better.

On other projects, the pickers will walk through freshly harvested cut-blocks and pick cones from the discarded tree tops laying around the block. It is important to note that picking operations usually happen in winter, so it can sometimes be pretty tricky moving through the blocks. Sometimes, pickers will need to work while using snowshoes, to facilitate getting around.

Of course, cone picking in the field is not the only source for nursery seed. Some licensees have their own orchards with trees that have been selected as genetically superior (don't confuse this with genetically modified), and seed is obtained from within the orchard. Seed for specific sites is selected based on its original elevation, and upon latitudes/longitudes. Deviation from these parameters has been shown to result in poorer survival and performance. A google search of "forest nursery" for your specific province will likely result in a number of useful results.

Fire Fighting

Fire Fighting/Suppression is an activity which can vary significantly from province to province. In British Columbia, for example, some fire fighters are hired on provincial government crews and work on a full-time basis, either fighting fires or on training/standby, whereas others are hired by contractors and may work for shorter periods, but with more activity, during the peaks of the season.

Being a member of a fire crew can often be an "all or nothing" situation. There will be times when there are no fires to be suppressed in your area, so your daily activities may be limited to lots of training and physical conditioning, and making sure your suppression equipment remains in good working order. During these times, many fire fighters may become slightly restless and bored. However, once a fire needs to be attacked, you'll find yourself working exhausting shifts, which involve a great deal of physical exertion.

Due to the nature of the work, fire suppression can be a more dangerous line of work than many other silviculture activities. Safety is highly emphasized in this field, as with other fields, but caution is always paramount when working on the fire line and also around equipment. Obviously, fire fighting work is a very seasonal activity, with almost all of the work taking place in May through September.

Other Related Forestry Activities

This section includes details about things like running site prep equipment, doing commercial thinning, brushcutting & mulching, erosion control, and carbon offset work.

There are a number of other forestry activities that directly impact the work of Silviculturalists, because they are so closely related to Silviculture. Running Site Prep (preparation) equipment is a good example. A Silviculturalist, or Silviculture Forester, will often look at a cut block and decide that the most effective way to maximize regeneration on the block will be to perform some sort of mechanical site preparation (site prep using machines, as opposed to having the planters perform hand/shovel/boot screefing). There are a wide variety of types of site prep, and generally, most of these are performed by either skidders, dozers, or excavators, which have various tools and attachments. Disc trenching happens when a skidder or excavator has two discs attached to the back, and as it travels across the block, the discs dig into the ground and flip sod and soil up and to one side, so a pair of two trenches are created across the block. These trenches are generally about a foot to two feet in size from the bottom of the trench to the top of the thrown debris, and trees are either planted in the bottom of the trench or up on the side, depending on the region. Ripper plows are generally a large tooth or plow impediment that is attached to a machine, and as it gets pulled across the block it rips a sort of trench open behind it to expose the soil. Dragging happens when a dozer drags a set of very large and heavy metal drums called shark-fin barrels across the block, and these barrels, with large teeth on them, have enough weight to really flatten and break up slash, and distribute it more evenly across a block. This is for a variety of reasons, which include making it easier to walk on the block, eliminating areas where slash makes it difficult to plant, spreading coarse woody debris around for future decomposition and fertilization of the future forest, and to help distribute and break up cones that will release seeds and assist with natural regeneration.

Other common types of site prep are usually performed by excavators. Excavator or Hoe mounds are made when an excavator digs a number of holes all of the block, and scoops out the dirt from each hole and flips it upside down beside the hole. The planter then plants a tree on the top of the exposed pile of dirt. These piles are often one to two feet in height and perhaps a couple feet across. This type of prep is a lot slower and more expensive than machines that can move quickly, like trenchers. However, excavators can generally work on steeper slopes than trenchers, and excavator mounds are generally a much more effective form of treatment in swampy or wet areas. Excavators sometimes also do a different type of prep, especially on slopes, called scrapes. The excavator rests the tines of the bucket on the ground and gently pulls back to create a rectangle of exposed mineral soil. When the planter arrives to the block later, he/she can plant a tree in the center of each exposed scrape. This is a good treatment that minimizes competition from grasses and nearby brush. There is also another type of mounding called donaren mounding, which is a sort of cross between excavator mounding and disc trenching. With donaren mounding, a pair of rotating scoops are attached to the back of a machine and it travels across a block quite quickly, flipping up two lines of smaller mounds. This type of mounding is especially effective on flatter blocks with lower slash loads. All of these types of mechanical site prep require heavy equipment training for operators. There are a large number of heavy equipment schools across Canada which have programs usually ranging from one to four months, and these schools will train operators on one or several pieces of equipment. In construction, the main four pieces are the front end loader, grader, excavator, and dozer, but in Silvicultural Site Prep, it is the excavator and dozen and skidder that are most important. In logging, excavators and dozers are important, but there are also a number of other specialized types of equipment such as delimbers, grapple yarders, forwarders, and harvesters.

Commercial thinning is a type of thinning that is performed well after a plantation has become established. It is similar to the juvenile spacing/thinning that was described above, but later in the life cycle of the plantation, once the trees are starting to become fairly large. At this point, there may be enough wood in the trees being cut that they can be useful in a commercial sense, perhaps for small lumber (2x4's) or more frequently for pulp & paper. A stand may be juvenile spaced five to fifteen years after being planted, but the commercial thinning might happen between twenty and thirty years after it is planted. Essentially, commercial thinning is a "pre-harvest" cutting which might pull out half of the trees for commercial use, instead of just dropping them on the ground and leaving them to rot. The remaining trees in the stand then have more room to grow properly to maturity. In a commercial thinning, the stand is too mature for brush saws, so chain saws and/or harvesting equipment is used to perform the thinning work.

Brushcutting and mulching are activities which are commonly associated with construction and maintenance of highways, right-of-ways, and power transmission corridors, rather than being associated with Silviculture. However, mulchers are sometimes effective in stands that were not planned/established correctly from the start, where a forester decides that the best approach is to start fresh. Mulchers are often able to plow through stands with trees of up to six inches in diameter or larger, and knock down the existing vegetation and mulch it into chips which are spread across the ground. A new plantation can then be established. Mulchers or chippers can also be used to mulch stands for bio-mass, to be used in various types of environmentally-friendly "green" energy generation.

Erosion control planning is sometimes a function of the Harvesting department, and sometimes a function of the Silviculture department. On any slopes, once a stand is harvested, there is always a risk that rain and surface run-off can wash soil away, which is very bad for the local watershed and for the health of the future stand. There are a number of ways to mitigate the effects of erosion, through methods such as cross-ditching, creating terraces, seeding, planting of brush and willows, installing culverts and drainage ditches, etc. Learning to protect a habitat from erosion is a fascinating challenge.

Carbon offset work usually involves planning and planting new stands on previously cut areas (reforestation) or on existing pasture or retired farmland (aforestation). The difference between these stands and stands designed for traditional logging cycles is that these are intended to be permanent stands. Rather than planting species which are intended to maximize commercial value for future generations, the goal may instead be to plant species which have the greatest amount of biomass and which can function most effectively to trap the greatest amount of carbon emissions.

Logging itself is also very closely related to Silviculture. Logging is the primary economic activity in the field of Forestry, and it is what provides the economic benefits that help society grow. Logging is also the primary reason why Silviculture is necessary: to bring harvested lands back to a state where they can be useful for future generations, either for wildlife, or for human recreational purposes, or for additional commercial exploitation. And there are many different activities within the logging/harvesting side of forestry. For example, some key functions that contribute to the overall process of logging include: Timber Cruising, Planning, Road Building, Harvesting, Hauling, Mill activities, and GIS (mapping and Geographic Information Systems) work.

In short, no matter what your interests or skills may be, there's probably a career within Silviculture or another branch of Forestry that will appeal to you!