Université du Québec en Abitibi-Témiscamingue, Rouyn-Noranda, Québec Canada SPRUCING UP EASTERN CANADIAN MIXEDWOODS: Do white spruce (Picea glauca) trees respond to partial cutting? Jessica Smith, candidate M.Sc. Biology B.Harvey PhD, A.Koubaa PhD, S.Brais PhD

INTRODUCTION Canadian Boreal Forest 90% of forested land in Canada British Columbia Newfoundland Quebec 1 (Baldwin et al., 2012)

Canadian Boreal Forest 90% of forested land in Canada Province of Québec Region: Abitibi–Témiscamingue 48°14'55.0"N 79°20'11.7"W Boreal Mixedwood Forest 2 INTRODUCTION

Boreal Mixedwood Forest Transitional phase of succession Shade intolerant broadleaf and shade tolerant conifers white birch (Betula papyrifera) trembling aspen (Populus tremuloides) white spruce (Picea glauca) black spruce (Picea mariana) balsam fir (Abies balsamea) shade intolerantshade tolerant Licher Stone Lane Gardens Tigner Fewless Maine Forest Service 3 (Bergeron and Harvey, 1997) INTRODUCTION

Boreal Mixedwood Forest Mature aspen: suitable for harvest Pre-mature white spruce: has not reached maximum growth potential white birch (Betula papyrifera) trembling aspen (Populus tremuloides) white spruce (Picea glauca) black spruce (Picea mariana) balsam fir (Abies balsamea) shade intolerantshade tolerant Licher Stone Lane Gardens Tigner Fewless Maine Forest Service 4 INTRODUCTION

Boreal Mixedwood Forest Mature aspen: suitable for harvest Pre-mature white spruce: has not reached maximum growth potential white birch (Betula papyrifera) trembling aspen (Populus tremuloides) white spruce (Picea glauca) black spruce (Picea mariana) balsam fir (Abies balsamea) shade intolerantshade tolerant Licher Stone Lane Gardens Tigner Fewless Maine Forest Service 4 INTRODUCTION

Why partial cutting? Ecosystem based management Diversify silvicultural strategies Emulate natural succession dynamics Maintain residual stand with complex structure and attributes Industry Residual trees show accelerated radial and volume growth rates following “release” Larger stems 5 (Youngblood, 1991; Yang, 1991; Man and Greenway, 2004; Grover et al. 2014) INTRODUCTION

Rouyn-Noranda, Abitibi–Témiscamingue, Québec, Canada Partial Cutting Treatments: 2002 Control 0% harvested 50% aspen BA harvested 65% aspen BA harvested 100% aspen BA harvested 3% balsam fir 1% black spruce 1% white birch 75% aspen 20% white spruce Pre-treatment species distribution by basal area Boreal Mixedwood Forest 6 STUDY SITE

Experimental Units 65% Control % % 52% % 74% 64% 100% Initial BA (m 2 · ha -1 ) Residual BA Aspen removed (m 2 · ha -1 ) % % % STUDY SITE

Evaluate radial and volume growth responses of residual white spruce trees, 10 years after the implementation of the partial cutting treatments 1. Post-treatment radial and volume growth rates will be higher in intermediate treatments (50% and 65%) than in the extreme treatment (100%) 2. Tree social status will influence post-treatment radial and volume growth rates, with dominant and co-dominant trees having superior growth rates to suppressed trees 8 OBJECTIVE HYPOTHESES

Experimental Design % 50% 0% 100% Scale 1:10,000 4 treatments 3 replications 12 Experimental Units trees 3 social status 6 Trees/ Experimental Unit 72 Trees METHODS

Sampling and Data Collection 1 (30 cm) (130 cm) 10 (Chhin et al., 2010) METHODS

Annual Ring Width Measurements Win Dendro (Regent Instruments) annual radial growth rate (mm·year -1 ) 3 radii per disk 5 years pre-treatment 10 years post-treatment Stem Analysis Win Stem (Regent Instruments) annual volume growth rate (dm 3 ·year -1 ) 11 METHODS

Statistical Analysis Linear mixed effect model Response VariableExplanatory Variables 1. Annual Radial Growth at 1.3 m (mm·year -1 ) 2. Annual Volume Growth (dm 3 ·year -1 ) Fixed effects treatment intensity social status time time 2 mean growth rate 5 years pre-treatment treatment intensity : time treatment intensity : time 2 social status : time social status : time 2 Random effects experimental unit tree number 12 METHODS

Annual Radial Growth 1.3 m A) Suppressed B) Co-dominant C) Dominant 13 RESULTS

Annual Radial Growth 1.3 m In the 100% aspen removal treatment, average annual radial growth rates at 1.3m were: 23.5% higher for dominant trees 67.7% higher for co-dominant trees 154.3% higher for suppressed trees as compared to the control treatment over the 10 year post-treatment period A) Suppressed B) Co-dominant C) Dominant 13 RESULTS

Annual Radial Growth 1.3 m C) 65% Aspen BA removal D) 100% Aspen BA removal A) ControlB) 50% Aspen BA removal 14 RESULTS

Annual Volume Growth A) Suppressed B) Co-dominant C) Dominant 15 RESULTS

Annual Volume Growth In the 100% aspen removal treatment, average annual volume growth rates were: 7.2% higher for dominant trees 24.1% higher for co-dominant trees 65.6% higher for suppressed trees as compared to the control treatment over the 10 year post-treatment period A) Suppressed B) Co-dominant C) Dominant 15 RESULTS

Annual Volume Growth C) 65% Aspen BA removal D) 100% Aspen BA removal A) Control B) 50% Aspen BA removal 16 RESULTS

1. Post-treatment radial and volume growth rates will be higher in intermediate treatments (50% and 65%) than in the extreme treatment (100%) 2. Tree social status will influence post-treatment radial and volume growth rates, with dominant and co-dominant trees having superior growth rates to suppressed trees Validating Hypotheses 17 RESULTS

1. Post-treatment radial and volume growth rates will be higher in intermediate treatments (50% and 65%) than in the extreme treatment (100%) 2. Tree social status will influence post-treatment radial and volume growth rates, with dominant and co-dominant trees having superior growth rates to suppressed trees Validating Hypotheses 17 RESULTS

2. Tree social status will influence post-treatment radial and volume growth rates, with dominant and co-dominant trees having superior growth rates to suppressed trees 1. Post-treatment radial and volume growth rates were higher in 100% aspen removal treatment Validating Hypotheses 17 RESULTS

2. Tree social status will influence post-treatment radial and volume growth rates, with dominant and co-dominant trees having superior growth rates to suppressed trees 1. Post-treatment radial and volume growth rates were higher in 100% aspen removal treatment Validating Hypotheses √ 17 RESULTS

1. Effect of partial cutting in 100% aspen removal treatment Annual Radial and Volume Growth 2. Treatment effect changes through time following a quadratic form Radial Growth: peaking 6 years post-treatment Volume Growth: plateau for suppressed and co-dominant trees, continuing linearly for dominant trees 4. Dominant and co-dominant trees superior to suppressed trees 3. Treatment effect across time is the same for all social statuses Relative growth increases greatest for suppressed trees, least for dominant trees, and intermediary for co-dominant trees CONCLUSIONS

2. Monitor regeneration and mortality 1.Remove high proportion of dominant, shade intolerant broadleaf species Savioja Schreiber 19 RECOMMENDATIONS

Fewless, Gary. Licher, Max. Maine Forest Service. Savioja,Jouko. Stone Lane Gardens. Tigner, Daniel. Canadian Forest Tree Essences. ColumnSubPage/ html Photos Arun Bose, Marc Mazerolle, Manuella Strukelj, Igor Drobyshev, Suzie Rollin, Fred Coulombe, Field Crew References Baldwin et al. Canadian Regional Team of the Circumboreal Vegetation Map Project. Natural Resources Canada, Canadian Forest Service, Great Lakes Forestry Centre (2012). Bergeron Y, Harvey B. Basing silviculture on natural ecosystem dynamics: an approach applied to the southern boreal mixedwood forest of Quebec. Forest Ecology and Management (1997) 92: Chhin S et al. Growth–climate relationships vary with height along the stem in lodgepole pine. Tree physiology (2010) 30: Grover et al. White spruce understory protection: From planning to growth and yield. The Forestry Chronicle (2014) 90: Man R, Greenway KJ. Meta-analysis of understory white spruce response to release from overstory aspen. The Forestry Chronicle (2004) 80: Yang R. Growth of white spruce following release from aspen competition: 35 year results. The Forestry Chronicle (1991) 67: Youngblood AP. Radial growth after a shelterwood seed cut in a mature stand of white spruce in interior Alaska. Canadian Journal of Forest Research (1991) 21: ACKNOWLEDGEMENTS