Lesson One - Introduction to Forest Stand Establishment

Forest stand establishment is a practice that ensures new healthy seedlings replace mature and over mature stands of trees as they are harvested. This Home Study Module will discus how natural and artificial regeneration techniques can maintain or improve the productivity of our woodlots by ensuring good stocking levels after harvest.

Successful stand establishment is the most important step toward good forest management. Without new seedlings, the site may not realize its full productive potential. It is similar to the carrot patch that has poor seed germination and produces more weeds than carrots; the garden is simply not as productive as it could be.

STOCKING

Stocking is the term used to describe whether there are enough trees per area and is usually expressed as a percentage. To better understand stocking, consider forest sites and stands as graphically comprised of square plots ( Figure 1 )

In Nova Scotia we usually plant seedlings and precommercially thin young stands to a spacing of approximately 1.8-2.4 metres (6-8 feet) between stems. Forest research indicates that these spacings are best for early tree growth and development for our average sites, tree species, and climate. Ideal spacing is 1.8m x 1.8m (6' x 6'), aiming for approximately 3,100 trees/hectare (1,210 trees/acre). This spacing provides young stands with 100 percent stocking and a good chance for survival during its first 40 years ( Figure 1 ). At narrower spacings, the trees have inadequate space and slow diameter growth. At wider spacings, the trees have too much space and will become limby and have less useable wood.

Each tree will develop and grow best if it is sufficiently free of competition from weeds and other trees for light, moisture and nutrients. When trees are taller than the competition, they are considered "free growing".

For plantations or naturally regenerated stands between one and 40 years of age, all plots must have one healthy, free growing tree for the site to be fully stocked ( 100%). A fully stocked area is fully utilized by growing as much wood as possible of a commercial tree species.

On the other hand, the site is only partially stocked if some plots are either barren or occupied by non-commercial species. Usually, partially stocked sites are expressed as a percentage. For example, if 1550 of the possible 3,100 plots/ha are occupied by commercial species, the site is 50% stocked and is only growing approximately 50% as much wood as possible.

However, openings on a woodlot may be desirable for wildlife. These areas will be used by many different species for feeding, hunting, and courting. Woodlots and Wildlife is the topic of Home Study Course Module IV.

In Nova Scotia, average sites with fully stocked stands can produce approximately one cord per acre per year for softwood species such as red spruce, balsam fir, and white spruce. Therefore, the softwood plantation or natural stand in ( Figure 1 ) should contain approximately 358 cubic metres/ha (40 cords/ac.) at 40 years. Hardwood trees produce less volume and generally fewer trees per acre than softwoods in a fully stocked stand because of the larger crown development. Softwoods have a more compact crown and use less energy to produce new needles annually.

It is important to understand stocking, site utilization, and the potential of sites to grow wood since these factors influence the establishment practices on our woodlots.

Cutting the forest without thinking about the next generation of trees can reduce the quality of the next stand. This cutting practice can develop into highgrading which removes the biggest and best trees and leaves poor quality trees to produce seeds. Highgrading is evident in all regions of Nova Scotia where there are now some stands of poor quality hardwood and softwood growing on sites previously occupied by more valuable species ( Figure 2 ).

Nova Scotia has approximately 30 native tree species. Ten of these will not be discussed because they are not common. Of the remaining 20 species, four have little commercial value, but play an important role in forest development and succession. They are striped maple, pin cherry, grey birch, and speckled alder.

Sixteen commercial species are listed in ( Figure 3 ), along with their relative percentages of total growing stock. Total growing stock is an estimate of the total standing wood volume in Nova Scotia. In 1987, this volume was estimated at 406 million cubic metres (112.3 million cords).

FOREST SUCCESSION

Have you ever wondered why one or several tree species occupy much of your woodlot? The answer may be that these trees are best suited and compete well in that particular woodlot environment. When discussing the environment of your woodlot, consider the climate, soils, topography, and site history. Together, these factors help determine the types of trees that grow on your woodlot.

Climate:
Is it hot or cold, wet or dry? As a very general example, Cape Breton Island and the Eastern Shore have hardy species such as balsam fir and black spruce because of a cool, damp climate and short growing season. Western Nova Scotia has a drier, warmer climate and a longer growing season which may favour red spruce, red oak, or white pine. The abundance of all native species varies throughout the province.

Soils:
Is the soil rocky? Does it contain well drained sandy loams or poorly drained clays, etc.? Pines regenerate, survive, and grow better on dry sites because they have a deeper rooting system than most conifers. They are commonly found on the dry, sandy loam of western Nova Scotia. Black spruce and larch can withstand excessive soil moisture better than other species and are found on many swampy areas throughout Nova Scotia. Black spruce and larch are also found on the better sites, but usually don't compete well with other species.

Topography:
Is your woodlot on a mountain top, close to a windswept seashore, or in a valley? Hardwoods are more likely to be found on ridges and hillsides, while softwoods are more likely to dominate valleys. Forests near shorelines are dominated by white spruce because they are able to withstand damage caused by wind and salt spray.

Site History:
Has your woodlot been burned, cut, farmed, or has it been undisturbed for the last 200 years? This history is often the major factor that relates to the present species and stand type. For example, white spruce regenerates quickly on abandoned fields and pastures throughout Nova Scotia, usually forming pure stands. It regenerates better than all other 19 tree species with grass on old fields or pastures. There is close to one million acres of white spruce on abandoned farmland in our province.

Most woodlots are usually made up of several stand types with various species and ages. Since artificial regeneration is a relatively new management tool in Nova Scotia, most stand types have become established from natural regeneration. These stands became established because the particular site history that existed favoured the development of certain species. In many areas you can stand on the boundary line separating two woodlots and see stands of completely different species composition; one side of the line can be 100% softwood and the other side 100% hardwood. The climate, soils, and topography on both sides of the line may be similar, but the site history has obviously been different.

Forest succession is the change in species composition, over time, as long-lived climax species replace short-lived pioneer species. There are several successional patterns in the forests of Nova Scotia. One example commonly found in the western area is shown in ( Figure 4 ).

In Nova Scotia there are many climax forest types made up of pure or mixed stands. Balsam fir dominates the climax forest types on the plateau of Cape Breton Island while red spruce dominates the climax forest types of mainland Nova Scotia.

The introduction of beech bark canker in the early 1900's has removed beech from the climax position that it once held. Sugar maple and yellow birch now occupy a climax position in our forests.

To help understand forest succession and why forests often change species after disturbance, 20 tree species are grouped into five classes, based on their ability to survive and grow in shaded conditions, known as shade tolerance ( Table 1 ). It is important to understand shade tolerance to understand where each species fits into forest succession. You will then begin to understand why your woodlot reacts and develops as it does over time. Please study Table 1 carefully.

The following is an example of how the shade intolerant-tolerant relationship works with natural succession.

In a two-story stand, shade intolerant species usually overtop the shade tolerant ones. On your next walk in your woodlot, compare the trees in the top canopy of a two-story stand to those in the bottom. You will generally find intolerant species such as aspen, white birch, or larch above balsam fir or red spruce. You will never find aspen, white birch, or larch growing under other trees.

( Figure 5 ) illustrates this situation and gives some of the reasons why shade intolerant species usually become established before shade tolerant ones.

Using the shade tolerance ratings in ( Table 1 ), our potentially most valuable trees occupy the middle to late stages of succession.
* intermediate species - white pine, white ash, red oak.
* tolerant species - red spruce, black spruce, white spruce, yellow birch
* very tolerant species - sugar maple
On the other hand, our least valuable trees for forest fibre products dominate the early stages of succession.
* intolerant species - white birch, aspen, larch, pin cherry, grey birch, alder

This explains why our forest management programs modify, as much as possible, the earliest stages of succession. This is accomplished by using either natural or artificial regeneration management techniques.

Forest management programs aim to produce healthy, productive forests capable of yielding increased volumes of high quality products. Consideration is also given to the maintenance of enhancement of fish and wildlife habitats, water quality, and recreational opportunities.

STAND ESTABLISHMENT IN NOVA SCOTIA

The main priority of our stand establishment practices is to ensure that the percentage of high value species is maintained or increased on our woodlots. In 1987, approximately 54 percent of our forest growing stock was made up of our most desirable species ( Table 2 ) .

From a stand establishment perspective, where do you begin? Start first by examining your land to see what is there. Does your woodlot have the following:

(1) old stands
(2) poorly stocked stands
(3) young, immature stands with species of very low value

If your woodlot has these types of stands, you may want to consider stand establishment techniques to improve productivity. The easiest way to get started may be to get help from forestry personnel from the Department Natural Resources, a Forest Group Venture in your area, or an approved forestry consultant. They can help develop a management plan for your woodlot. The plan will identify similar stand types and provide for your woodlot. The plan will identify similar stand types and provide information on species composition, tree heights, ages, percent stocking, wood volume per area, stand condition, maturity, and regeneration stocking by species.

Typical stands that should be replaced with more valuable tree species are:

(1) "Old" stands (mature-overmature)

Example:
Balsam fir and white spruce stands will normally show a significant decline in growth by 40 years and may be considered mature. At age 60, they are usually overmature and may have started to deteriorate.

Trees can live longer than the average ranges outlined in ( Table 3 ). However, at some point they begin to decline, resulting in butt rot, dead tops, blowdown, and reduced height and diameter growth. At the older stage, it is more productive to harvest and ensure that the trees are replaced with healthy, young trees of good desirable species. The old saying "the timber on my woodlot is as good as money in the bank" may or may not be true, depending on whether your forest stands are growing (appreciating in value) or declining (depreciating in value).

(2) "Poorly stocked" (understocked) stands of any age

Example:
A well stocked stand of red spruce 40 years old will normally have 3,100 trees per hectare. A 40 year old red spruce stand that has had only 741 trees per hectare from the beginning will be poorly stocked stands should be replaced, regardless of species.

(3) Immature stands with "low value" species

Example:
Immature grey birch and aspen stands have very low commercial value and limited market opportunities in Nova Scotia. This is not likely to improve in the future. If these stands occupy a significant portion of the woodlot, it may be the best to salvage any usable wood and restock the site with more valuable species.

Now that we have a general idea of which stands should be considered for stand establishment techniques, and assuming our objective is to grow primarily the most valuable species, what are the alternatives? How should clearcuts, partial cuts, shelterwood, or seed tree treatments be used? Should we plant after cutting or will natural regeneration restock the site?

The next two lessons will attempt to answer these questions by describing the common mature to overmature stand types on small woodlots in Nova Scotia and how to regenerate them.