Natural Range of Variability estimates

for forest vegetation growth stages of

Minnesota’s Drift and Lake Plains

Lee E. Frelich

Final Version, April 16, 2000

 

Tamarack Swamp

Successional rules:

Rotation period for wind: 100-350 years

Rotation period for fire: 100-200 years

Fire returns any VGS to the seedling stage

Wind can return the pole-mature or old-growth stages to the seedling stage

Stand maintenance disturbances occur but do not affect successional trajectory

 

VGS

Age

Range of variability (%) of

landscape

Seedling tamarack

1-20

12.8-24.4

Sapling-pole tamarack

21-55

18.8-31.2

Pole-mature tamarack

56-75

9.4-12.9

Old growth tamarack

>75

31.5-59.0

 

Forested Bog

Successional rules:

Rotation period for wind: 200-400 years

Rotation period for fire: 100-200 years

Fire returns any VGS to the seedling stage

Wind can return the pole-mature or old-growth stages to the seedling stage

Stand maintenance disturbances occur but do not affect successional trajectory

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling black spruce

1-35

19.4-31.4

Sapling-pole black spruce

36-75

18.7-26.0

Pole-mature black spruce

76-160

23.8-23.9

Old growth black spruce

>160

18.8-38.0

 

Forested Poor Fen

Successional Rules:

Rotation period for wind, 200-400 years

Rotation period for fire, 200-400 years

Fire will return any VGS to the seedling-sapling stage

Wind will return pole-mature or old growth to the seedling-sapling stage

Stand maintenance fires occur but do not affect successional trajectory

 

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling tamarack

1-35

13.7-23.0

Sapling-pole tamarack-black spruce

36-75

14.4-22.2

Pole-mature tamarack-black spruce

76-100

8.0-11.1

Old growth tamarack-black spruce

>100

43.8-63.9

White cedar swamp

Successional Rules:

Rotation period for wind, 200-400 years

Rotation period for fire, 400-800 years

Fire will return any VGS to the seedling-sapling tamarack stage

Wind will advance pole-mature tamarack-cedar, and return mature or old growth cedar-spruce to seedling-sapling cedar-spruce

Stand maintenance fires occur but do not affect successional trajectory

Spruce refers to a mixture of black and white spruce

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling tamarack

1-55

6.5-12.2

Sapling-pole tamarack

56-75

2.3-4.2

Pole-mature tamarack-cedar

76-100

2.6-4.4

Seedling-sapling cedar-spruce

1-30

5.9-9.5

Sapling-pole cedar-spruce

31-55

4.7-7.4

Mature cedar-spruce

56-110

13.5-18.4*

Old-growth cedar-spruce

>110

43.9-64.5

*Can be separated into 56-75 and 75-110 age classes as follows:

56-75: 5.0-6.8

76-110: 8.5-11.6

Semiterrestrial cedar forest

Successional Rules:

Rotation period for wind, 200-500 years

Rotation period for fire, 1000-2000 years

Fire will return any VGS to the seedling-sapling aspen-birch-spuce-tamarack stage

Wind will advance pole-mature aspen-birch-cedar, and return mature or old growth cedar-fir-birch to seedling-sapling cedar-fir-birch

Stand maintenance fires occur but do not affect successional trajectory

Spruce refers to a mixture of black and white spruce

 

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling aspen-birch-spruce-tamarack

1-25

1.2-2.4

Sapling-pole aspen-birch-spruce-tamarack

26-55

1.5-2.9

Pole-mature aspen-birch-spruce-cedar-tamarack

56-75

0.9-1.7

Seedling-sapling cedar-fir-birch

1-25

4.3-9.1

Sapling-pole cedar-fir-birch

26-55

5.2-10.8

Mature cedar-fir-birch

56-110

11.2-19.1*

Old-growth cedar-fir-birch

>110

53.9-75.7

*Can be separated into 56-75 and 75-110 age classes as follows:

56-75: 4.2-7.0

76-110: 7.0-12.1

 

Semiterrestrial black ash forest

Successional Rules:

Rotation period for wind, 200-500 years

Rotation period for fire, 1000-2000 years

Fire will return any VGS to the seedling-sapling stage

Wind will return pole-mature or old growth to the seedling-sapling stage

Stand maintenance fires occur but do not affect successional trajectory

 

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling black ash-balsam poplar

1-20

4.5-9.3

Sapling-pole black ash-balsam poplar-elm

21-55

7.6-15.6

Pole-mature black ash-elm

56-120

12.6-21.6

Old-growth black ash

>120

53.5-75.3

Lowland hardwood-conifer forest

Successional Rules:

Rotation period for wind, 250-500 years

Rotation period for fire, 300-600 years

Fire will return any VGS to the seedling-sapling aspen-birch stage

Wind will advance pole-mature birch-conifer or return pole-mature and old-growth conifer to the conifer seedling-sapling stage

Stand maintenance fires occur but do not affect successional trajectory

Conifer refers to a mixture of white pine, white spruce, cedar and fir

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling aspen birch

1-15

4.7-6.2

Sapling-pole aspen-birch

16-35

6.0-8.0

Pole-mature aspen-birch-conifer

36-75

9.2-14.0

Seedling-sapling conifer

1-15

2.4-4.5

Sapling-pole conifer

16-35

3.1-5.7

Pole-mature conifer

36-75

15.9-17.5

Mature-large conifer

76-175

22.9-32.0

Old-growth conifer

>175

16.8-31.0

Rich hardwood forest

Successional Rules:

Rotation period for wind, 300-600 years

Rotation period for fire, 1000-2000 years

Fire will return any VGS to the seedling-sapling birch-aspen stage

Wind will advance pole-mature birch-aspen-pine, mature-large birch-pine-maple, old-growth pine-mapleor or return pole-mature maple and large maple old growth to the seedling-sapling maple stage

Stand maintenance fires slightly lengthen the time spent in the mature-large birch-pine -maple and pine-maple stages.

Conifer refers to white pine and fir

 

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling birch-aspen

1-15

0.7-1.5

Sapling-pole birch-aspen-conifer

16-35

1.0-1.9

Pole-mature birch-aspen-conifer

36-75

1.8-3.3

Mature-large birch-maple-conifer

76-120

1.9-3.1

Old-growth pine-maple

120-195

2.7-3.9

Old-growth maple

>195

48.1-67.4

Seedling-sapling maple

1-15

2.3-4.2

Sapling-pole maple

16-35

3.1-5.6

Pole-mature maple

36-75

5.6-9.5

Large maple

76-195

13.5-18.8

Mesic northern hardwood forest

Successional Rules:

Rotation period for wind, 1000-2000 years

Rotation period for fire, 1000-2000 years

Fire will return any VGS to the seedling-sapling birch-aspen stage

Wind will advance pole-mature birch-pine-aspen, mature-large birch-pine-maple, or return old-growth maple, pole-mature maple or large maple to the seedling-sapling maple stage

Stand maintenance fires slightly lengthen time spent in the mature-large birch-pine-maple, old-growth pine-maple stages.

 

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling birch-aspen

1-15

0.7-1.5

Sapling-pole birch-aspen

16-35

1.0-1.9

Pole-mature birch-pine-aspen

36-75

1.9-3.6

Mature-large birch-pine-maple

76-120

2.1-3.7

Old-growth pine-maple

121-195

3.2-5.3

Old-growth maple

>195

69.1-82.7

Seedling-sapling maple

1-15

0.7-1.4

Sapling-pole maple

16-35

1.0-1.8

Pole-mature maple

36-75

1.8-3.4

Large maple

75-195

5.0-8.2

Mesic oak brushland-savanna-forest

Successional Rules:

Rotation period for wind, 1000-2000 years

Rotation period for fire, 500-1000 years

Surface fire, 5-10 years, with 0.1 or 0.2 annual chance, sets savanna stage or seedling oak-aspen forest stage back to the grass-brush stage

Fire will return any VGS to the grass-brush stage

Wind will return pole-mature, mature-large aspen-oak pine, old multi-aged pine-oak and old pine-maple-oak seedling-sapling aspen-oak stage

 

 

 

VGS

Age

Range of variability (%) of

landscape

Grass-brush

1-15*

19.4-57.1

Savanna

16-35*

9.5-14.2

Seedling-sapling aspen-oak

1-35*

2.7-3.7

Sapling-pole aspen-oak pine

36-75

2.7-4.0

Pole-mature aspen-oak-pine

76-115

2.5-3.8

Mature-large aspen-oak-pine

116-140

1.4-2.3

Old multi-aged pine-oak

141-195

16.8-49.4

Old maple-pine-oak

>195

2.6-7.9

*Model has two different successional pathways. The grass-brush-savanna pathway has frequent fires that prevent succession with random annual chance of 0.1 (10-year fire return) or 0.2 (5-year fire return). Those stands that escape from the grass-brush-savanna route (no fire for 30 years) get into the forest pathway and have a separate stand age, starting from the time of the last fire (either a surface fire that maintained the gras-brush or savanna or forest fire that set forest back to grass-brush). Another way of stating all this is that there are two alternate 1-35 year old states that coexist--one grass-brush-savanna and one the seedling-spaling aspen-oak.

Dry-mesic pine-oak forest

Successional Rules:

Rotation period for wind, 1000-2000 years

Rotation period for fire, 250-500 years

Surface fire, 40 years, can set mature-large aspen-pine red maple-oak, multi-aged red maple-pine-oak or old red maple-oak back one stage.

Fire will return any VGS to the seedling-sapling aspen-jack pine-oak stage

Wind will return pole-mature aspen-pine-red maple-oak, mature-large pine-oak-red maple, multi-aged red maple-pine-oak or old red maple-red oak to the seedling-sapling stage

Pine refers to mixed jack, red and white pines

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling aspen-pine -oak

1-15

3.6-6.8

Sapling-pole aspen-pine-oak

16-35

4.6-8.5

Pole-mature aspen-pine-red maple-oak

36-75

32.8-34.8

Mature-large pine-red maple-oak

76-120

24.4-26.6

Multi-aged red maple-pine-oak

121-175

16.0-19.8

Old red maple-red oak

>175

9.3-12.6

Dry-mesic pine forest

Successional Rules:

Rotation period for wind, 500-1000 years

Rotation period for fire, 175-350 years

Surface fires, 30 years, slow rate of successional advancement

Fire will return any VGS to the seedling-sapling stage

Wind will return pole-mature aspen-pine-oak, mature-large red-white pine and multi-aged red-white pine to the seedling-sapling stage

Pine refers to jack pine and red/white pine mixture

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling aspen-pine-oak

1-15

6.0-11.0

Sapling-pole aspen-pine-oak

16-35

8.4-14.5

Pole-mature aspen-pine-oak

36-75

12.9-19.4

Mature-large red -white pine

76-175

24.0-27.1

Multi-aged red-white pine

>175

28.0-48.7

Dry pine forest

Successional Rules:

Rotation period for wind, 1000-2000 years

Rotation period for fire, 60-120 years

Surface fire, 40 years, slows rate of successional advancement

Fire will return any VGS to the seedling-sapling jack pine-aspen stage

Wind will return pole-mature jack pine-aspen, multi-aged pine or multi-aged red and white pine to the seedling-sapling stage

Pine refers to mixed jack, red and white pines

 

 

VGS

Age

Range of variability (%) of

landscape

Seedling-sapling jack pine-aspen

1-15

12.8-22.8

Sapling-pole jack pine-aspen

16-35

15.8-24.0

Pole-mature pine-aspen

36-75

20.5-24.0

Multi-aged pine

76-175

20.3-26.8

Multi-aged red-white pine

>175

9.0-24.1