Lesson Two - Natural Regeneration Management

Natural regeneration develops when seeds from surrounding trees fall to the forest floor or stump sprouts and root suckers develop on some hardwoods. This and other methods of reproduction are illustrated in ( Figure 6 ). To regenerate our forest stands naturally, it is necessary to understand the strategy for survival of each tree species.


For each tree species we need to know:

  1. At what age will a particular tree begin producing seed crops?
  2. How often do good seed years occur?
  3. How far can seeds travel from the parent tree either by wind, squirrels or birds?
  4. Once on the forest floor, how long will the seed remain good (viable) - a few weeks? a year? several years?
  5. What type of seed bed is preferred by each species? How much moisture is required?
  6. How much sunlight (full versus partial) is required to keep seedlings alive and growing? Are young seedlings usually present as advanced regeneration in mature and overmature stands?
  7. Is the species capable of vegetative reproduction (sprouts, suckers)?
  8. Using the answers to these questions, what cutting strategy can be used to ensure that the new stands will contain sufficient numbers of our preferred species?

Table 4 ( One + Two ) helps answer these questions by providing information for seven preferred species, as well as two aggressive competitors. If this all seems to complicated, we will help you so that it won't be complicated at all.

The requirements for healthy seedling production for the seven preferred species are very similar. In general:

  1. With the exception of yellow birch and sugar maple, they all begin producing good seed crops between 40-50 years of age. Smaller amounts of seed can usually be produced before these ages. Obviously, if stands are cut before optimum seed-bearing age, the chances of regenerating these species are reduced.
  2. With the possible exception of red spruce, we can expect good seed crops at least every five years. This is not a long time in the life of a forest.
  3. Most species have seed which are small enough to be carried by wind up to several hundred feet from the parent tree. Red oak seed are too large to be windblown.
  4. Their seeds all mature in early fall and spend the winter on the forest floor. Germination will occur in the following spring if the seed is good and it has landed on a suitable seedbed. Seeds are usually good for one year with the exception of black spruce, white ash, and yellow birch. Black spruce cones open slowly and can protect the seed so it may remain viable for several years, while yellow birch and white ash may remain viable for two years.
  5. All seven species are intermediate to very tolerant of shade. Except for pure stands of white spruce and black spruce, these species will regenerate from seed with some form of shelterwood system.
  6. All species prefer mineral soil beds, but frost heaving can be a problem. A mixture of mineral soil and humus is the preferred seedbed because it is less likely to dry out in the summer and is the best medium for roots to extract nutrients and water. Sugar maple and white ash have an advantage with their large taproots that can penetrate leaf litter on the forest floor, whereas the other species cannot. Skidding with horses and winching with farm tractors or skidders is an excellent way to mix mineral soil with humus in shelterwood cuts.

These points show some of the similar characteristics which exist for the seven tree species covered in Table 4. As summarized, most of these species will regenerate after some form of shelterwood system. However, this does not eliminate the possibility of using alternate forms of clearcuting, selection, or seed tree systems.

The final decision would also need to consider other information; such as, the woodlot owner's objectives and the required volumes or stocking levels needed for the treatment to be successful.

Clearcutting is the most common method of harvest. It can provide an opportunity for other tree species listed in Table 4. In 1987, red maple made up 15 percent and balsam fir made up 18 percent of the total growing stock in Nova Scotia and both are increasing at the expense of more valuable species.

Let's summarize the factors from Table 4 that enable red maple and balsam fir to be so competitive.

Red Maple

Balsam Fir

Unlike red maple which starts quickly after disturbance, balsam fir's strategy for survival usually begins long before any disturbance takes place. Balsam fir produces seed at an earlier age than most of its competitors. The seedlings can survive for many years in the understory of most of our forest stands, ready to take advantage of any openings created in the overstory.

If you want to reduce balsam fir and red maple on your woodlot, practice shelterwood cutting to ensure adequate regeneration of other tolerant species. Later, precommercial thinning of the young trees can favour the most desirable species.

If your area is dominated by balsam fir, you may want to adopt a modified management strategy to optimize the use of this species.

Let's now discuss the different cutting systems that are available to establish natural regeneration. The following descriptions of the shelterwood, clearcutting, selection, and seed tree methods are simplified versions of those previously discussed in the Woodlot Management Homestudy Course entitled " Harvesting Systems. "

As a good example, the shelterwood system will be discussed in slightly more detail to illustrate the establishment of natural regeneration.


The following is a simplified version of shelterwood cutting as previously discussed in the Home Study Course module entitled Harvesting Systems.

Shelterwood cutting is the removal of mature timber in two or three partial cuts which extend over 10-20 years. The system encourages evenaged regeneration of preferred species under the partial shade of valuable seed trees. ( Figure 7 ) illustrates the shelterwood cutting system.

The 30-50 percent basal area removed in the first cut is designed to:

To better understand the effect of shading on the forest floor, compare the edge of a 5-10 year old clearcut to a dense stand of shade tolerant trees ( Figure 8 ). Forest stands along roadways can also provide an excellent opportunity to view the benefits of shading.

Shelterwood cutting uses partial shading to give the more valuable species the competitive edge at the seedling stage. When the seedlings become well established, the overstory can be removed. Well established softwood seedlings are at least 0.3 m (1 ft) tall with firm roots in mineral soil. The seedlings are now able to hold their own against the competition and grow best under full sunlight.

Shelterwood cutting is a very good way to promote natural regeneration of desirable species. Here are some guidelines that can improve the prospects for success.

Pre-cut Stand Assessment:

Walk through the stand before you begin cutting. Note the regeneration; check the forest floor closely since some seedling, such as red spruce, are very small. Also note potential seed sources of the most valuable species. Assess site and stand conditions and make a mental plan of how you will proceed to :(a) minimize damage to existing desirable regeneration and (b) encourage additional regeneration establishment. Refer to ( Figure 8 ) for help.

First Cut:

Second Cut

Final Cut

Follow-up Treatments

Conduct a weeding operation within 3-5 years of the final harvest. Cut stump sprouts and other regeneration of above average height that overtop the desirable regeneration. Leave 1-2 stems per stump to help control resprouting ( Figure 10 ). It is important to delay this weeding operation until the sprouts and suckers begin to seriously interfere with seedlings.

Finally, since these naturally regenerated stands will usually have too many seedlings for good stand growth and tree form, a precommercial thinning may be required. A precommercial thinning generally starts when the trees are 2 m (6 ft) tall in stands dominated by softwoods and 6m (20ft) tall in stands dominated by hardwoods. It is best to wait longer before spacing hardwoods to let the crop trees develop at least one log length of clear wood. Hardwoods are spaced wider than softwoods because they are older when thinned and additional space is needed to maintain good diameter growth.


Clearcutting is the removal of all, or most, of the trees on a piece of forested land during one harvest operation. It is the most common method of harvest used in Nova Scotia.

Clearcutting is an evenaged form of management because most of the trees that are cut are the same size and age.

Fortunately, our climate is very favourable for tree growth. As such, 67% of all clearcuts regenerate naturally to commercial species. In those areas that either do not or cannot regenerate naturally, artificial regeneration may be needed.

When applied properly, clearcutting is a safe and effective way to manage your stands. It is suited to stands of overmature trees; areas extensively damaged by fire, insects, diseases, or wind;; and stands that have been highgraded or are composed of poor quality trees. Before clearcutting, an assessment should be made of the existing regeneration and a forecast made for possible seedling establishment after the cut.

Alternate clearcutting methods also include strip and patch cuts which encourage natural regeneration establishment. As previously noted, more information on these alternatives is given in an earlier Home Study Course module.


Selection cutting is the removal of trees from a stand to provide a steady flow of forest products from the woodlot. This unevenaged management system can remove single trees, groups of trees, or strips of trees from a stand. It differs from shelterwood cutting and clearcutting which are evenaged management systems.

Selection management should not be confused with diameter-limit cutting in which trees less than a certain diameter are not harvested. This can result in "high-grading" where you "take the best and leave the rest" because the small trees are not always young ones.

Selection cutting is a complicated system which combines aspects of shelterwood cutting, precommercial thinning, and merchantable thinning to maintain stands with trees in at least three age classes.

Unfortunately, selection management has its disadvantages. Compared to the even-aged cutting practices, this system requires more skill when selecting trees to be cut. Selected trees need to be good quality, tolerant, and long-lived (80+ years) species that are windfirm and able to survive with less than full sunlight.

An extensive road and trail network are also required to remove the low volumes on each acre.

If you want to try the selection system on your woodlot, ask forestry personnel for help.


This method of stand establishment is a modification of clearcutting, except that scattered good quality, mature trees are left to provide seed for a new crop.

This system can be used very successfully to regenerate white pine in Nova Scotia. For white pine, leave 20-30 good quality, healthy seed trees per hectare (8-10 trees per acre), preferably in semi-straight rows, to make future cutting of the seed trees easier when regeneration becomes well established. White pine is suited to this system because it is a very windfirm species.

The follow factors allow white pine to regenerate and compete after clearcutting:

  1. Its intermediate shade tolerance allows it to compete with species such as raspberry, pin cherry, and hardwood sprouts which usually regenerate clearcuts.
  2. It usually grows on poor, dry sites where there is less competition with other tree species and shrubs than is on fertile sites.

Regardless of which harvesting system is used to promote natural regeneration, it is important to do a pre-cut stand assessment to determine which system is best for your woodlot.


Here are some examples of common mature and over mature stand types that are suitable for natural regeneration management and the results that can be expected from a shelterwood cut.

Red Spruce Stands

Red spruce is a valuable tree in Nova Scotia. It responds well to natural regeneration management. Stands may be pure red spruce or comprised of at least 30 percent red spruce.

Sample stand types are:

As ( Table 3 ) in Lesson 1 indicates, red spruce usually matures in 80-100 years. There are a few situations where red spruce stands begin to deteriorate at 40-50 years. In these stands, shelterwood cutting should be started early. These include:

  1. some old pasture lands where red spruce has developed excessive butt rot
  2. stands in poor health because of porcupine or insect damage
  3. stands with greater than 40 percent short lived species, such as balsam fir, aspen, and larch.

Where it occurs naturally in Nova Scotia, red spruce regenerates well when the shelterwood method is used. Usually, the forest floor under mature red spruce stands is covered with tiny red spruce seedlings from previous seed years. Our major objective in these stands is to ensure adequate sunlight for good seedling growth. In many cases, the first and second cuts of the shelterwood system can be combined and the period from the initial to the final cut may be within 5-10 years. In stands where red spruce is mixed with shade tolerant species such as eastern hemlock and sugar maple, crown closure is usually so tight that red spruce regeneration is unlikely to become established. In this situation, the shelterwood process will require three cuts as noted in ( Figure 7 ).

In red spruce stands with a high proportion of balsam fir, the regeneration may be dominated by the more competitive and generally larger balsam fir seedlings. A precommercial thinning which favours red spruce can change this situation. In some instances, young stands with high proportion of balsam fir can be converted to primarily red spruce. For example, a 1.8 x 1.8 metre (6 ft. x 6 ft.) plot may have nine balsam fir seedlings and one red spruce seedling before precommercial thinning, but only the red spruce seedling after precommercial thinning.

Red spruce does not occur extensively on Cape Breton Island because of the generally harsh, cool climate. Some red spruce planted on well drained, sheltered sites, such as inland valleys, is expected to grow reasonably well.

There are many hardwood stands that are well stocked with red spruce regeneration of various sizes. The seeds may have come from scattered reed spruce trees either in the stand, in red spruce stands nearby, or in many cases, from the trees that were removed.

Gradually opening these stands through shelterwood cutting will allow them to convert to predominantly red spruce. These types of stands show us the importance of pre-cut assessments for good stand establishment techniques.

Balsam Fir Stands

These stands may be pure stands of balsam fir or stands where balsam fir is the major species.

Sample stand types are:

Balsam fir stands tend to develop well after a clearcut since advanced regeneration is usually present. This regeneration is present because balsam fir produces seed at an early age and generally begins to deteriorate before reaching 40. Only in limited areas, such as the Cape Breton Highlands, can balsam fir remain healthy for longer periods of time.

Shelterwood cutting is not necessary for balsam fir stands. To establish a stand on a woodlot dominated by balsam fir, you could:

White Pine Stands

These are pure stands or mixed stands where white pine comprise a major component.

Sample stand types are:

White pine regenerates very well in Nova Scotia when one of the following systems are used:

  1. shelterewood system
  2. clearcutting with seed trees (20-30 trees/ha or 8-12 trees/acre)
  3. clearcutting immediately following a good seed year

Intermediate in shade tolerance, white pine seed can germinate and grow under partial shade created by the shelterwood system or under full sunlight created by clearcutting. Adequate soil disturbance provided by skidding or winching will help improve regeneration results, regardless of which system is used.

White pine weevil is a very serious pest that usually makes its home in the leaders of the largest, fastest growing trees. Affected trees become crooked and are generally worthless. When these stands are between 6-9 metres (20-30 feet) tall, a precommercial thinning can reduce the impact of weevil damage. Cut the deformed trees and favour straight-stemmed, co-dominant and intermediate trees, spacing the trees approximately 2-3m (6-10 ft) apart.

White pine has traditionally been a valuable tree. Managing individual trees or stands of white pine by using good stand establishment techniques, weevil control, thinning, and pruning to produce clear wood may bring worthwhile benefits to woodlot owners in the future.

Tolerant Hardwood Stands

These may be pure stands of sugar maple or stands of sugar maple mixed with yellow birch, beech and lesser amounts of red maple, white birch, white ash, eastern hemlock, red spruce, and striped maple.

Sample stand types:

Our general objective in managing these stands is to grow straight, clear stems of sugar maple, yellow birch, and white ash to a diameter of 30-35 cm (12-14 in.). Hardwood logs reach their maximum value when the diameters are equal to or greater then about 32 cm (13 in.). Fully stocked tolerant hardwood stands with an average diameter of 32 cm (13 in.) will have approximately 350 trees/ha (140 trees/ac.).

These species usually begin to mature at 80 years ( Table 3 ), at which point regeneration establishment can be considered at an earlier age for poor quality stands with less than 200 stems/ha (80/ac) of yellow birch, sugar maple, and white ash.

Sugar maple and white ash have large seeds and require similar seedbeds. Their seedlings can penetrate hardwood leaf litter (matts). Yellow birch has very small seed and may require some soil disturbance provided by skidding or winching trees to create suitable exposed mineral soil.

( Figure 7 ) gave a general idea of the shelterwood cutting method presently recommended in Nova Scotia. In hardwood stands, more volume is removed in the first cut than from softwoods. With hardwoods, the release cut can be omitted in favour of the final cut when the average height of the regeneration is 0.5-1.0m (1.5-3 ft.). The ideal time for the final cut is when most seedlings are more than 0.5m (1.5 ft.) tall and have shown growth of at least 15 cm (6 in.) during the previous growing season. These seedlings will be well established and will no longer need the benefit of overhead shade, but are still small enough the risk of damage during final felling will be low.

Since sugar maple, white ash, and red maple are vigorous stump sprouters, sprout control is very important if the new stand is to be well stocked with young trees of seed origin. Sprouts can quickly outgrow seedlings. Three years after final harvest, a sprout may be 3m (10 ft.) while a seedling may be about 0.5-1.0m (2-3 ft.).

Expect young hardwood stands to be approximately 12 meters (40 ft.) tall at 40 years, at which time a second thinning will be required to maintain good diameter growth.