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 th June, 2014

Introduction to the eastern boreal mixedwood

Early successional species Trembling aspen Populus tremuloides Jack pine Pinus banksiana White birch Betula papyrifera Photo: CM Bouchard

Introduction to the eastern boreal mixedwood Early successional species Trembling aspen Populus tremuloides Jack pine Pinus banksiana White birch Betula papyrifera Mid- to late-successional species White spruce Picea glauca Black spruce P. Mariana Balsam fir Abies balsamea Eastern white cedar Thuya occidentalis Photo: CM Bouchard

Introduction to the eastern boreal mixedwood Early successional species Trembling aspen Populus tremuloides Jack pine Pinus banksiana White birch Betula papyrifera Mid- to late-successional species White spruce Picea glauca Black spruce P. Mariana Balsam fir Abies balsamea Eastern white cedar Thuya occidentalis Woody shrub Mountain maple Acer spicatum

6 Natural dynamics of mixedwood stands

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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 Edmonton Calgary Toronto Montréal Ottawa Halifax

Lake Duparquet Forest study sites SAFE 1 (1923) SAFE 3 (1910)

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

12 years after, Bose, A. K. et al Recruitment and mortality dynamics following partial harvesting in aspen-dominated mixedwoods in eastern Canada. For. Ecol. Manag. In press. Bose, A. K. et al 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: Short-term results of the experiment 3 years after, Brais, S. et al 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: years after, Harvey, B.D. and Brais, S 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:

Simulator The SORTIE-ND 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% BA61% BA Control 80% BA 400 m 2 (37% BA)900 m 2 (43% BA)1600 m 2 (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

Results (White spruce dynamics)

SAFE-1SAFE-3 TreatmentsStand BA% of ConifersStand BA% of Conifers Control 27.1± ± % dispersed cut 26.9± ± % dispersed cut 27.9± ± % dispersed cut 32.7± ± m 2 gap cut 32.6± ± m 2 gap cut 33.8± ± m 2 gap cut 38.0± ± Simulation results at year 100

Conclusions 1.Model validation o Good short-term validation for controls and low intensity partial cut o 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

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

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 Thank you for listening !! SORTIE-ND for the boreal mixedwood forest: a work in progress....