Modelling stand dynamics after partial harvesting in eastern Canadian boreal mixedwoods

1. 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

2. Introduction to the eastern boreal mixedwood

3. Introduction to the eastern boreal mixedwood Early successional species Trembling aspen Populustremuloides Jack pine Pinusbanksiana White birch Betulapapyrifera Photo: CM Bouchard

4. Introduction to the eastern boreal mixedwood Early successional species Trembling aspen Populustremuloides Jack pine Pinusbanksiana White birch Betulapapyrifera Mid- to late-successional species White spruce Piceaglauca Black spruce P. Mariana Balsam fir Abiesbalsamea Eastern white cedar Thuyaoccidentalis Photo: CM Bouchard

5. Introduction to the eastern boreal mixedwood Early successional species Trembling aspen Populustremuloides Jack pine Pinusbanksiana White birch Betulapapyrifera Mid- to late-successional species White spruce Piceaglauca Black spruce P. Mariana Balsam fir Abiesbalsamea Eastern white cedar Thuyaoccidentalis Woody shrub Mountain maple Acer spicatum

6. Natural dynamics of mixedwood stands Succession 1st cohort 2nd cohort 3rd cohort Intolerant broadleaves Mixedwood Tolerant conifers

7. Natural dynamics of mixedwood stands Fire Succession 1st cohort 2nd cohort 3rd cohort Intolerant broadleaves Mixedwood Tolerant conifers

8. Natural dynamics of mixedwood stands Spruce Budworm Gaps Fire Tent caterpillar 1st cohort 2nd cohort 3rd cohort Intolerant hardwoods Mixedwood Tolerant softwood Partial harvesting, a tool of Natural Disturbance Based Management

9. Study site Supraboreal (Taïga) Mesoboreal (Continuousconifer) Thermoboreal (Mixedwood) Edmonton Study site, Lake Duparquet Research & Teaching Forest ≈ 48° N 79° W Vancouver Calgary Source: Baldwin et al. (2013) Halifax Montréal Ottawa Toronto

10. Lake Duparquet Foreststudysites SAFE 3 (1910) SAFE 1 (1923)

11. Initial stand condition SAFE 1 (1923) Acer spicatum SAFE 3 (1910) Abies balsamea

12. Short-termresults 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 (Populustremuloides) dominated boreal mixedwoods : implications for deadwood dynamics. Can. J. For. Res. 37: 1525-1533. 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 (PopulustremuloidesMichx.) volume growth in the boreal mixedwood: Effect of partial harvesting, tree social status, and neighborhood competition.For. Ecol. Manag. 327: 209-220.

13. 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)

14. SORTIE-ND Model • Spatially-explicit • position of eachtreedefined • growth • recruitment • mortality • Permits simulation of • complex mixed-species stands • partial cuts • all forms and types of openings(gaps, patch cuts)

15. Model calibration • 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 Blais1981) • Field data were used to set starting conditions of simulations

16. Objectives To evaluate whether SORTIE-ND capture short and long term stand dynamics To identify partial harvesting prescriptions that accelerate the development of multi-cohort complex stands To assess whether mixedwood stands of different composition respond similarly to partial harvesting treatments over a period of 100 years after harvesting

17. Testing partial cutting scenarios Initial condition: empirical data, n=15 Control Dispersed partial cuts 33% BA 61% BA 80% BA Gap cuts 400 m2 (37% BA) 900 m2 (43% BA) 1600 m2 (54% BA)

18. Results (Model validations) Short term (12 years) validation, empirical and simulated results showed excellent agreements for un-harvested controls and low-light intensity partial harvesting treatments However, disagreements appeared with high-heavy intensity partial harvestings on overstory aspen survival Higher uncertainties appeared with long-term (78 years) model validation, particularly on aspen recruitment and spruce survival

19. Results (Trembling aspen dynamics) Gap cuts & 80% dispersed Gap cuts & 80% dispersed Gap cuts & 80% dispersed Gap cuts & 80% dispersed

20. Results (Balsam fir dynamics) Sprucebudwormoutbreakincidents Sprucebudwormoutbreakincidents

21. Results (White spruce dynamics)

22. Simulation results at year 100

23. Conclusions • Model validation • Good short-term validation for controls and low intensity partial cut • Long-term validation, • Aspen: problems with recruitment • Spruce: juvenile recruitment and survival too high • SORTIE-ND does project feasible outcomes that appear to incorporate influences of different treatments and stand conditions

24. Conclusions • Objective-2 • Layout 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-3 • Starting 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

25. SORTIE-ND for the boreal mixedwood forest: a work in progress.... Thankyou for listening !! Acknowledgements NSERC-FQRNT-BMP Scholarship BC Forest Service, Bulkley Valley Research Center Lora Murphy, Albanie Leduc, Danielle Charron, Marc Mazerolle, Mario Major, Manuella Strukelj, Jeanne Therrien, Suzie Rollin, Hannah Brais-Harvey, Elizabeth Turcotte, Alfred Coulombe