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Forest Renewal Standards

Hardwood
Renewal Standards
:

Free to Grow Standards:

pdf iconDownload the Forest Renewal Standards document
pdf iconDownload the "Application of Free to Grow Standards" document

 

Defining the Hardwood Renewal Standards

Provincial Hardwood Renewal Standards have been developed for hardwood regeneration in Manitoba. These standards identify the amount of hardwood regeneration required to sufficiently regenerate hardwood dominated harvest blocks, and indicate the type of forest each harvest block could potentially develop into. The hardwood renewal standards are applicable on even aged areas following clear-cutting, scarification, seeding or planting. Failure to achieve the appropriate renewal standard for the site indicates the need for reforestation activity (planting, replanting).

The standards reflect the number of trees required at the end of the renewal period to produce a forest stand similar in species composition to the stand prior to harvest. The number of trees required was calculated using survival rates derived from the results of studies. Hardwood survival rates range between 65 and 74 percent during ten year intervals for aspen stands.

Regression curves were used to determine stocking levels that would reflect the number of stems required at the end of the regeneration period to produce a forest similar in species composition to the pre harvest stand.  These regression curves express the specific stocking and density relationships that have been developed from regeneration survey results for each species (black spruce, jack pine and white spruce).

natural regeneration: pine seedling
Natural jack pine regeneration

Two categories of standards have been identified; one for hardwood blocks regenerating naturally and one for hardwood dominated blocks that have been planted with softwood seedlings (Table 1).

The specific standard to apply is determined by the pre harvest species composition, for example a hardwood dominated harvest block should regenerate to the provincial hardwood standard.

For each site some latitude in the forest renewal standard to be achieved is allowed because of the approximations involved. The number of trees in mature stands of the same cover type, the subtypes identified by the Forest Resource Inventory, and the stocking required to produce mature forest stands are all approximations. Harvest blocks will be deemed sufficiently regenerated if they achieve the forest renewal standard which matches the cover type of the original stand or either standard immediately above or below the original stand.

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Hardwood Natural Regeneration

Naturally regenerated hardwood ("N" and "H") sites should achieve the forest renewal standard that relates to the previous cover type that occupied the site. The sites will be deemed sufficiently regenerated if they achieve the forest renewal standard which matches the cover type of the original stand or either standard immediately above or below the original standard. If they do not achieve these standards the sites are considered not sufficiently regenerated even though they may be forested.

Table 1. Forest renewal standards for hardwood natural regeneration
("N" and "H" sites)

Original Site
Black Spruce
"N" Sites
Jack Pine
"N" Sites
White Spruce
"N" Sites
Forest Renewal Standard

Softwood Stocking

Total Stocking Softwood Stocking Total Stocking Softwood Stocking Total Stocking
Mixedwood "M" ≥40% ≥70% ≥25% ≥70% ≥35% ≥70%
Mixedwood "N" ≥15% ≥80% ≥15% ≥80% ≥25% ≥80%
All Hardwood Sites "H" n/a ≥80% n/a ≥80% n/a ≥80%


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Defining The Free To Grow Standards

Softwood Free To Grow

The description of a 'free to grow' tree is a well established softwood tree which is free from hardwood competition and is at least 1.5 metres from other free to grow trees.

A free to grow (FTG) tree must not have any hardwood stems that are >66 percent the height of the free to grow tree within the competition threshold distance for that species. Research in Manitoba (MacIsaac 1995) has determined the threshold distance between a hardwood competitor and a softwood crop trees beyond which crop trees are free to grow is 1.0m for spruce and 1.25m for pine.

Hardwood trees outside the plot must be considered in the selection of free to grow trees. Hardwoods less than one metre tall (ie. not tallied in stocking assessment) may also render softwood trees not free to grow.

Surveyors may use their own discretion to classify some trees as 'not free to grow' if shrubs within the plot or branches from trees outside the competition threshold distance overtop the top third of the crop tree.

The softwood free to grow standards indicate the minimum number of acceptable, well spaced, free growing softwood trees per hectare.

The formula used to determine the number of FTG stems per ha for an individual species is as follows:

FTG stems per ha = # of FTG stems ÷ total plots x 250

It is expected that sites classified as softwood "S" by Manitoba's forest resource inventory prior to harvest or sites that have been planted to softwoods will meet the softwood FTG standard.

Table 2 Softwood FTG Standards

Site Description
Black Spruce
Pine
White Spruce
Original FRI
Subtype Code
13 - 17
01 - 06
10 - 11
Number of
FTG stems per ha
800
730
510

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Mixedwood Free To Grow Standards

The mixedwood free to grow standards indicate the minimum number of acceptable, well spaced softwood trees per hectare and total hardwood trees per hectare. It is expected that sites classified as mixedwood "M" by Manitoba's forest resource inventory prior to harvest will meet the mixedwood FTG standard.

Table 3 Mixedwood FTG Standards

Site Description
Black Spruce
Pine
White Spruce
Original FRI
Subtype Code
53 - 58
41 - 49
50 - 51
Number of well spaced (WS) softwood stems per ha
1120
860
850
Number of hardwood stems per ha
2000 - 4000
2000 - 4000
2000 - 4000


Application Of The Free To Grow (FTG) Standards 


The provincial FTG standards indicate the status of each block surveyed. The total number of trees per hectare may be much higher. Sites will be described in one of several classifications based upon the FTG survey results.

The reforestation goal for sites originally classified as softwood and sites planted to softwood is to achieve the FTG-S standard. The reforestation goal for sites originally classified as mixedwood is to achieve the FTG-M standard.

Free To Grow Softwood (FTG -S-spp)

  • enough well spaced, black spruce, jack pine or white spruce, FTG stems to ensure the site will develop into a softwood forest

Free To Grow Mixedwood (FTG-M-spp)

  • enough well spaced black spruce, jack pine or white spruce stems and total hardwood stems so that the site will develop into a predominantly softwood mixedwood stand

Not Free To Grow Mixedwood (NFTG-M-spp)

  • enough well spaced black spruce, jack pine or white spruce stems to meet the FTG-M standard but with enough hardwood stems so that the site will develop into a predominantly hardwood mixedwood stand

Not Free To Grow Softwood (NFTG-S-spp)

  • enough well spaced black spruce, jack pine or white spruce stems worth releasing so that the site will develop into a softwood forest

Mixedwood N

  • enough well spaced softwoods (spruce or pine) and total hardwoods to ensure development to mixedwood forest

Hardwood

  • enough hardwood to develop into hardwood forest

Softwood Regeneration (REGEN-spp)

  • enough black spruce, jack pine or white spruce regeneration for a site to potentially develop into a mature softwood forest although there are not enough well established conifers to meet the Softwood or Mixedwood M FTG standards

NSR

  • insufficient hardwoods or softwoods to develop into fully stocked forest


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