Modelling stand dynamics after partial harvesting in eastern Canadian boreal mixedwoods

Arun K. Bose, Brian D. Harvey, Dave K. Coates, Suzanne Brais, Yves Bergeron

9th IUFRO International Conference on Uneven-aged Silviculture, WSL, Zurich, Switzerland

17-19th June, 2014

Introduction to the eastern boreal mixedwood

Introduction to the eastern boreal mixedwood

Early successional species

Trembling aspen Populus tremuloides

Jack pine

Pinus banksiana

White birchBetula papyrifera

Introduction to the eastern boreal mixedwood

Early successional species

Trembling aspen Populus tremuloides

Jack pine

Pinus banksiana

White birchBetula papyrifera

Mid- to late-successional species

White spruce Picea glauca

Black spruceP. Mariana

Balsam firAbies balsamea

Eastern white cedarThuya occidentalis

Introduction to the eastern boreal mixedwood

Early successional species

Trembling aspen Populus tremuloides

Jack pine

Pinus banksiana

White birchBetula papyrifera

Mid- to late-successional species

White spruce Picea glauca

Black spruceP. Mariana

Balsam firAbies balsamea

Eastern white cedarThuya occidentalis

Woody shrub

Mountain maple

Acer spicatum

6

Natural dynamics of mixedwood stands

Intolerant broadleaves Tolerant conifers1st cohort 3rd cohort2nd cohort

Mixedwood

Succession

7

Natural dynamics of mixedwood stands

Intolerant broadleaves Tolerant conifers1st cohort 3rd cohort2nd cohort

Mixedwood

Succession

Fire

Intolerant hardwoods Tolerant softwood1st cohort 3rd cohort2nd cohort

Mixedwood

Fire

8

Tent caterpillar

Spruce Budworm

Natural dynamics of mixedwood stands

Gaps

Partial harvesting, a tool of Natural Disturbance Based Management

Study site

Source: Baldwin et al. (2013)

Thermoboreal (Mixedwood)

Mesoboreal (Continuous conifer)

Supraboreal (Taïga)

Study site, Lake Duparquet Research & Teaching Forest ≈ 48° N 79° W

Vancouver

EdmontonCalgary

Toronto

MontréalOttawa

Halifax

Lake Duparquet Foreststudy sites

SAFE 1(1923)

SAFE 3(1910)

Acer spicatum

5 7 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40+0

20

40

60

80

100

120

140

Aspen Birch Fir Spruce Jack pine

DBH class (cm)

Basal area (m2/ha)Aspen: 41Spruce:1Birch: 1Fir: <1J. pine: <1

SAFE 1(1923)

5 7 10 12 14 16 18 20 22 24 26 28 30 32 34 36 38 40+0

20

40

60

80

100

120

140

Aspen Birch Fir Spruce

DBH class (cm)

Basal area (m2/ha) Aspen: 34 Spruce: 6Fir: 2Birch: <1

SAFE 3(1910)

Abies balsamea

Initial stand condition

12 years after, Bose, A. K. et al. 2014. Recruitment and mortality dynamics following partial harvesting in aspen-dominated mixedwoods in eastern Canada. For. Ecol. Manag. In press.

Bose, A. K. et al. 2014. Trembling aspen (Populus tremuloides Michx.) volume growth in the boreal mixedwood: Effect of partial harvesting, tree social status, and neighborhood competition. For. Ecol. Manag. 327: 209-220.

Short-term results of the experiment

3 years after,Brais, S. et al. 2004. Testing forest ecosystem management in boreal mixedwoods of northwestern Quebec: initial response of aspen stands to different levels of harvesting. Can. J. For. Res. 34: 431-446.

6 years after,Harvey, B.D. and Brais, S. 2007. Partial cutting as an analogue to stem exclusion and stand break-up in aspen (Populus tremuloides) dominated boreal mixedwoods : implications for deadwood dynamics. Can. J. For. Res. 37: 1525-1533.

Simulator

The SORTIE-ND http://www.sortie-nd.org/research/pubs.html

A spatially explicit individual-based model

Originally developed and parameterized for hardwood forests in the northeastern United States (Pacala et al., 1993, 1996)

Re parameterized for British Columbia forests (Coates et al. 2003)

105 peer-reviewed publications since 1993 (SORTIE-website)

• Spatially-explicit– position of each tree defined

– growth

– recruitment

– mortality

• Permits simulation of– complex mixed-species stands

– partial cuts

– all forms and types of openings (gaps, patch cuts)

SORTIE-ND Model

• Growth, mortality and recruitment functions were tested for each individual species

• Mortality by spruce budworm was implemented using knowledge of published literatures (Morin et al, 1993; Bergeron and Leduc,1995 and Blais 1981)

• Field data were used to set starting conditions of simulations

Model calibration

Objectives

1. To evaluate whether SORTIE-ND capture short and long term stand dynamics

2. To identify partial harvesting prescriptions that accelerate the development of multi-cohort complex stands

3. To assess whether mixedwood stands of different composition respond similarly to partial harvesting treatments over a period of 100 years after harvesting

Testing partial cutting scenarios

33% BA 61% BA

Control

80% BA

400 m2 (37% BA) 900 m2 (43% BA) 1600 m2 (54% BA)

Dispersed partial cuts

Gap cuts

Initial condition: empirical data, n=15

Results (Model validations)

1. Short term (12 years) validation, empirical and simulated results showed excellent agreements for un-harvested controls and low-light intensity partial harvesting treatments

2. However, disagreements appeared with high-heavy intensity partial harvestings on overstory aspen survival

3. Higher uncertainties appeared with long-term (78 years) model validation, particularly on aspen recruitment and spruce survival

Results (Trembling aspen dynamics)

Gap cuts & 80% dispersed

Gap cuts & 80% dispersed

Gap cuts & 80% dispersed

Gap cuts & 80% dispersed

Results (Balsam fir dynamics)

Spruce budworm outbreak incidents

Spruce budworm outbreak incidents

Results (White spruce dynamics)

SAFE-1 SAFE-3

Treatments Stand BA % of Conifers Stand BA % of Conifers

Control27.1±2.5

51.323.7±1.2

78.5

33% dispersed cut26.9±2.4

44.622.9±1.1

79.5

61% dispersed cut27.9±2.5

35.823.1±1.9

78.4

80% dispersed cut32.7±2.1

17.724.9±2.8

66.3

400 m2 gap cut32.6±1.9

29.828.7±1.2

47.0

900 m2 gap cut33.8±1.6

21.630.8±1.4

38.6

1600 m2 gap cut38.0±0.8

17.634.1±1.9

27.6

Simulation results at year 100

Conclusions

1. Model validationo Good short-term validation for controls and low

intensity partial cuto Long-term validation,

o Aspen: problems with recruitment o Spruce: juvenile recruitment and survival too high

o SORTIE-ND does project feasible outcomes that appear to incorporate influences of different treatments and stand conditions

ConclusionsObjective-2Layout of the harvesting is the KEY

Gap cut would promote both conifers and intolerant hardwood regeneration

Gap cut would allow higher basal area retention Higher basal area retention would also provide

greater habitats for animals

Objective-3Starting condition is the KEY

Age of the overstroy trees Seed trees of desired conifer species Stock of advanced regeneration of desired conifer

species Presence of woody shrubs

AcknowledgementsNSERC-FQRNT-BMP ScholarshipBC Forest Service, Bulkley Valley Research CenterLora Murphy, Albanie Leduc, Danielle Charron, Marc Mazerolle, Mario Major, Manuella Strukelj, Jeanne Therrien, Suzie Rollin, Hannah Brais-Harvey, Elizabeth Turcotte, Alfred Coulombe

Thank you for listening !!

SORTIE-ND for the boreal mixedwood forest: a work in progress....