Management
Objectives for Mature Coniferous Forests
Before writing a prescription for a harvest
area, the general management objectives must be outlined. In coniferous forests of the North East, we
include for discussion the following five broad management goals.
We have produced this decision key to act
as a tool to identify stands that are suitable for non clear-cut harvesting.
This requires defining some simple objectives and identifying stand
structural data for inputs to the key. Depending
on management objectives and stand conditions, the cutting cycle is either
a form of reproduction cutting, including planting and thinning if required,
or an intermediate cutting.
Each management objective is discussed in
terms of the stand information required to achieve the objective. An assessment
of this stand information will evaluate the suitability of the stand to accomplish
the desired management objectives. Specific
objectives of individual managers or particular stand combinations, features
or opportunities, can with some integrity be incorporated into specific prescriptions.
The management objectives for mature conifer forests include:
1.
Capture of Imminent Mortality / Conservation of Growing Stock
In naturally overdense immature to mature
forests, volume often dies and is lost before harvesting operations can take
place. This objective is accomplished by using partial
cutting operations as a method of entering more stands at an earlier date,
thus capturing this volume that would be missed at later periods. Data inputs includes species composition and
a tree vigor classification that identifies it as imminent mortality. Tree class guidelines as defined
by McLintock (1958) and found in the Silvicultural
Guide for Spruce-Fir in the Northeast (Frank & Bjorbom, 1973)
are a good starting point. For our
purposes tree "stability class" should differentiate between imminent
mortality, and stability rating or index. In other words tree available for
cutting on the first pass and trees suitable to be left for the later
fellings.
There is also the assumption in wood supply
modeling that practices which minimize volume loss and maintain current growing
stock, in anticipation of the new forest, will mitigate negative impacts of
the wood supply shortage. ( Baskerville pers. comm.) Certainly much modeling
work must be here to evaluate and quantify these relationships.
2. Promotion of Natural Regeneration Favouring Desired Species and Protection of Advanced Regeneration
Natural methods to achieve regeneration are inherent to the silvicultural systems, hence the similarly used term reproduction systems. Essentially, silvicultural goals predict post cutover response. The best place to start is with the pre-cut condition or advanced regeneration status. In some cases this may require the characterization of the development stages, if the stand contains more than simply a mature “overstory” associated with a regenerating “understory”. In the prescriptions associated with a recommended silvicultural system, cut pecking order guidelines are essential in accomplishing objectives. In addition to examples of those submitted in some of the reviewed guides, the following cut pecking order guidelines are proposed for incorporation into the prescriptions to achieve natural regeneration favouring spruce.
Cut Pecking Order Guidelines
In a mixed spruce / fir regeneration, perhaps the best stage to favour spruce over fir is during pre-commercial thinning. Pre-commercial thinning is a effective and critical step to achieve improved spruce composition.
In some stands transition from mature to
regenerating development stage, each cut must be economically and biologically
viable. To evaluate this, information regarding initial volumes, product /
species distribution, and tree vigor or stability rating is required. If the precut survey reveals minimal volumes,
insufficient for economic viability for more than one cut, or unsuitable stand
or site quality , then the stand should not be considered for multiple-pass
harvesting. Biological considerations
dictate that imminent mortality be removed in the first cut, therefore only
trees that are able to fulfill their planned function(s); for example as a
seed or shelter source, and are sufficiently stable to remain until the planned
objective has been achieved, are to be left for the second, final felling. A typical first cutting of a two pass operation
will be the removal of between 30 to 50 percent of the initial, moribund volumes.
(often called the prep cut or first phase of a shelterwood cutting, followed
by a final felling after natural regeneration has become established
4. Promotion
of Value Added Products / Improve Low Grade Markets
Management for
value added products, such as sawlogs, in the future can be done by leaving the reserves, ie. Medium
sized or studwood sized, healthy spruce at the second stage of the two-pass
harvesting operation. This possibility
should be verified by noting the presence of
suitable candidate trees during the precut survey. It would appear that the shelterwood and seed
tree system could be very effective for managing sawlogs in the future. (Let us assume that any logs we are ever going
to harvest are growing now) Leaving studwood sized seed trees through their
primary seeding function, through pre-commercial thinning of the new stand,
to the next intervention is plausible.
This process has
been referred to as "banking potential sawlogs" for use at higher
values at a later date. Many forms of reproduction or intermediate cutting
could accomplish this. Firm expanding markets must be found for the low grade
products generated in the first cut, in order to permit economic viability
and obtain optimum utilization of the resource. In the right stands commercial
thinning promotes sawlog growth. Significant rate differentials between products
would promote good utilization practices, thus improving profitability.
5.
Non-Timber Management
Objectives
Primarily, the
objectives and inventory component of prescription harvesting, focus on operational,
timber management functions at the stand level.
However, many non-timber values are influenced and manipulated with
responsible applications of silvicultural techniques, although more rigorous
data collection efforts and methods may be required for some of these values.
Many of these alternative needs are yet to be defined or worked into a precut
survey format. For example, in the
case of deer, at the stand level, the critical components that deer require
are functional winter shelter near appropriate food sources.
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