1. L8 Post-disturbance succession in boreal forest
Dr. Han Chen
Office: BB-1009F
Phone:
Reading material
Chen, H.Y.H., S. Vasiliauskas, G.J. Kayahara, and T. Ilisson Wildfire promotes broadleaves and species mixtures in boreal forest. Forest Ecology and Management 257:
Ilisson, T., and H.Y.H. Chen Response of six boreal tree species to fire and clearcutting. Ecosystems 12:
Ilisson, T., and H.Y.H. Chen The direct regeneration hypothesis in northern forests. Journal of Vegetation Science 20:
Senici, D., H.Y.H. Chen, Y. Bergeron, and D. Cyr Spatiotemporal variations of fire frequency in central boreal forest. Ecosystems 13:
FORE3215, L5

2. Questions How frequent is fire in central boreal forest?
How forest composition change after disturbance? –post-disturbance succession

3. Spatiotemporal fire regimes
What is the fire cycle in central boreal forest?
Does fire cycle change with time?
Does fire cycle change spatially?
Parisien & Moritz. 2009, Ecol Monogr 79: )
FORE3215, L5

4. The Forest and Methods
Burn rate
Dendro-chronology
11,600-km2

5. Time period investigated
Temporal regimes
Method
Time period investigated
Burning rate
N/A
158
Inverse hazard
150 ( )*
295 ( )
96 (84-111)
140 69

6. Spatial drivers for fire
Variable
Full Model
Prob > χ2
FF ratio
Latitude
0.041
2.203
Longitude
0.105
0.619
Soil Order
0.004
1.78
Surficial Deposit
0.96
1.025
Mean Firebreak Distance
0.011
1.382
Aspect (west-east axis)
0.794
0.971
Aspect (north-south axis)
0.377
0.903
Elevation
0.19
0.997

7. What is the fire cycle in central boreal forest?
Approximately 100 years for the period of , but shorter (69 years) for , much longer (295 years) for
Changes spatially, longer
for stands closer to water bodies
in south (due to fire suppression and landscape fragmentation)
Brunisols (more likely dominated by broadleaves and mixedwoods)
Intermediate to east and west boreal forests (75 vs. 150 years), supporting climatic top-down control

8. Context-Postfire succession
Does a postfire stand have the same species composition as the prefire stand?
Yes! Based on Direct Regeneration Hypothesis
Proposed by Hanes (1971)
Recognized in fire-prone Mediterranean and Chaparral ecosystems

9. Direct regeneration in boreal forest
Species-specific post-fire regeneration density is proportional to its pre-fire basal area (Greene & Johnson Can. J. For. Res. 29: )
A pure post-fire aspen stand may be expected when the pre-fire stand has  20% aspen (Foresters’ prediction)
FORE3215, L5

10. Drivers Propogule availability (seeds, root suckers, or stem sprouts)
Substrates
Competitive ability
Species-specific prefire basal area
Fire variability within a burn

11. Questions
Can DRH be used in boreal forest? Do different tree species respond in a similar way?
Is fire intensity as a result of fire season and weather important in affecting postfire regeneration?
Used build-up index

12. Sampling A wide range of stand conditions on uplands
A wide range of fire season, thus build-up index
Prefire stands were mature and of naturally origin with no silvicultural treatments
Plots > 100 m from fire edges

13. Burns between 5 to 20 years

14. Field measurement Prefire stand Postfire regeneration
Determined by snags and down woody debris in a 400 m2 circular plot
Basal area by species
Stand age by counting rings of least shade tolerant species
By three 25 m2 circular subplots
Species
Height class

15. Characteristics of postfire sites
Prefire dominance
# of sites
Age of burn (yrs)
Prefire stand age (yrs)
Prefire basal area (m2/ha)
Jack pine 18
7.3 (2.8)
107 (43)
23.9 (7.3)
Trembling aspen 16
7.3 (2.3)
109 (53)
26.1 (9.1)
White birch 17
8.2 (3.3)
151 (52)
17.5 (6.5)
Black spruce 32
10.1 (4.2)
139 (45)
16.3 (5.6)
White spruce 6
6.8 (1.5)
154 (47)
23.7 (6.9)
Balsam fir 5
7.8 (0.4)
165 (69)
17.3 (9)

16. Species-specific postfire regeneration density

17. Regeneration density and buildup index
Jack pine
Trembling aspen
White birch
Black spruce
White spruce
Balsam fir

18. Other covariates for postfire regeneration density
Age of burn (5-20 yrs) affected positively black spruce regeneration density, and also marginally white birch and balsam fir
Moist sites had marginally greater jack pine regeneration density than dry and fresh sites when other factors (i.e., prefire jack pine basal area and BUI) are equal
Distance to fire edge and prefire stand age were insignificant

19. Can we conclude now?
Postfire regeneration density is linearly related to prefire basal area for jack pine, trembling aspen, white birch, and black spruce, not for white spruce and balsam fire
Build-up index also positively affect postfire regeneration for early successional species
Deep burn creates better substrates for regeneration of seed origin and perhaps reduces shrub competition for both sexual and asexual regeneration
But
This has not address DRH (i.e., the postfire stand has same compositions as the prefire)

20. Definition of CD
For a given species, compositional difference between the postfire and prefire stand (CD)
= Relative postfire regeneration density – Relative prefire basal area
DRH CD = 0

21. Species-specific responses

22. CD in relation to prefire composition

23. Conclusions DRH is true for jack pine
Fire promotes trembling aspen and white birch in the expenses of black spruce, white spruce, and balsam fir
Fire promotes species mixtures

24. Postfire stand type distribution based on prefire stand type

25. Postfire and post-clearcutting succession
Do post-disturbance regeneration behave in a similar way after fire and logging?
Ilisson, T., and H.Y.H. Chen Response of six boreal tree species to fire and clearcutting. Ecosystems 12:

26. Ilisson & Chen. 2009. Ecosystems 12: 820-829D
0.872 BA
<0.001
D x BA
0.57 D
0.969 BA
<0.001
D x BA
0.137 D
0.009 BA
0.001
D x BA
0.676 D
<0.001 BA
0.692
D x BA
0.865 D
0.117 BA
0.149
D x BA
0.226 D
0.006 BA
<0.001
D x BA
0.364
Ilisson & Chen Ecosystems 12:

27. Postfire and postlogging composition**

28. Post-disturbance succession conclusions
All stand-replacing disturbances promote broadleaves and species mixtures
Direct regeneration is applicable only to species with serotinous cones (e.g., jack pine and lodgepole pine)
Future landscapes will be more dominated by broadleaves because of a shorter fire return intervals

29. How does wind disturbance differ from fire and clearcutting
Ilisson, T., and H.Y.H. Chen The direct regeneration hypothesis in northern forests. Journal of Vegetation Science 20:

30. Direct regeneration hypothesis in northern forests
Q1: How do species regeneration strategy and/or shade-tolerance influence compositional development after stand replacing fire, clearcutting and wind disturbances?
Q2: Does disturbance type have effect?
A meta-analysis of 21 studies in northern forests

31. Regeneration strategy
Species
Broadleaves with strong vegetative reproduction ability
SV-B
Betula papyrifera, Populus balsamifera, P. grandidentata, P. tremuloides, Prunus serotina, Caraya spp, Quercus ellipsoidalis, Q. alba, Q. macrocarpa, Q. rubra, Acer rubrum, A. negundo, A. saccharum, Fagus grandifolia, Ostrya virginiana
Broadleaves with weak vegetative reproduction ability
WV-B
Betula lenta, B. nigra, B. alleghaniensis, Fraxinus nigra, F. americana, Prunus pennsylvanica, Ulmus americana, U. rubra, Tilia americana
Conifers with serotinous cones
S-C
Pinus banksiana, P. contorta
Conifers with semi-serotinous cones
SS-C
Picea mariana
Conifers without serotinous cones
NS-C
Larix laricina, Pinus resinosa, P. strobes, Picea glauca, Abies balsamea, Tsuga canadensis, Thuja occidentalis

33. Conclusions – Direct regeneration hypothesis in northern forests
Species regeneration strategy defines the success/failure of species after disturbances, less so does disturbance type
A species’ ability to regenerate vegetatively enables domination over species with other regeneration strategies
Data lacking for serotinous and semi-serotinous species after clearcutting