Nursery production of high quality aspen seedlings: The impact of growth environment on seedling stock

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1 Nursery production of high quality aspen seedlings: The impact of growth environment on seedling stock Jeff WG Kelly, Simon M Landhäusser, Pak S Chow University of Alberta

2 Outline Background Focus area Oil sands Boreal forest reclamation Seedling quality Important seedling characteristics for oil sands reclamation Study Light quantity Light quality Sheltering

3 Background Oil sands Land area open to oil sands leases covers ~20% of Alberta* Oil production projected to double over the next 20 years* Large footprint Reclamation and closure Source: *

4 Oil sands and forest reclamation Certification Issued only when longterm monitoring demonstrates the reclaimed land meets the objectives of equivalent land capability Only 0.15% of total area disturbed by oil sands mining currently certified as reclaimed

5 Difficulties associated with land reclamation Change in Soils Structure / Composition Texture Depth / Layers Nutrients Water holding capacity Vegetation Invasive species Weeds Exposure Photo credit: Laura Kennedy, U.S. Fish and Wildlife Service

6 Seedling quality Why is it important? Operationally Lowering of initial planting densities Financially Limit follow up costs Re-planting Monitoring How is quality determined? Survival and growth Given site / region Species specific

7 Desired seedling / species characteristics for oil sands land reclamation Broad tolerance to a range of site conditions Wide distribution Fast growth Stress tolerant Drought Temperature Nutrients Contribute to litter layer and forest floor material Availability Photo credit: Roth & Ramberg Photography, Syncrude Canada.

8 Trembling aspen (Populus tremuloides) Widest distribution in North America Wide genetic variability Adapted to a wide range of sites Fast growth Large accumulation of leaf and forest floor litter Regenerates from seed or by root suckering Drought tolerant Distribution U.S. Department of the Interior, U.S. Geological Survey

9 Trembling aspen in land reclamation Seedling characteristics High root to shoot ratio* Greater access to water and nutrients High carbon reserves* Insurance against poor growth conditions *Landhäusser et al. 2012

10 Aspen seedling quality Storage reserves Favored by anything that - Increases photosynthesis Decreases growth Decreases rates of maintenance respiration Applied techniques Moisture stress Increase light Decrease nutrients Decrease temperature Lower seedbed density

11 Aspen seedling quality study Grown from locally collected seed Transferred outdoors Treatments Light quantity Full-sun or shaded Light quality Shaded full-spectrum Blue Red Low R:FR Sheltering Sheltered or unsheltered

12 Objectives To identify the growth light environment, for aspen seedlings, which best promotes a High root to shoot ratio High root non-structural carbohydrates (NSC) To test whether pre-exposure to stressful conditions may serve as the driver for desired characteristics in aspen High light and fluctuations in temperature and VPD

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15 Methods Plant dimensions Height Basal diameter Gas exchange Photosynthesis Stomatal Conductance Quantum yield of PSII Biomass allocation Seedlings harvested after 6 months of growth Leaf Stem - Root Carbohydrate and nutrient content Stem Root

16 Results Height cm Sheltered *** Unsheltered ns c Shaded ab Blue Light ** b Red Light a Low R:FR Basal diameter mm Unsheltered * Sheltered ns Shaded Blue Light ns Red Light Low R:FR

17 30 ns 25 *** ns A mol m 2 s Photosynthesis Increased under full-sun 5 0 Unsheltered Sheltered Shaded Blue Light Red Light Low R:FR Signs of stress Full-sun Decreased quantum yield of PSII Decline in stomatal conductance PSII ns ** ab a * b ab Leaf level Full-sun Increased leaf temperature Unsheltered Sheltered Shaded Blue Light Red Light Low R:FR Increased VPD

18 Root NSC (% dry weight) Unsheltered ns Sheltered ns Shaded Blue Light ns Red Light Low R:FR Root to shoot ratio g g Unsheltered * Sheltered ns Shaded Blue Light ns Red Light Low R:FR Root carbon reserves Suggested benchmark > than 30% Root to shoot ratio Suggested benchmark > than 2

19 Treatment effects Light quantity and quality Minimal effect on growth or storage reserves Light levels (~90 and 45% of full sun) sufficient to minimize growth and storage differences Light quality height growth, storage reserves Sheltering Unsheltered - root to shoot ratio, storage reserves Combined effects of environmental stressors Increased wind, temperature, VPD and light

20 Utility to reclamation Preparation for harsh reclamation environments Predispose aspen seedlings to environmental stressors Grow seedlings outside Expose to - High light Increased winds Temperature fluctuations Fluctuations in VPD Increased water stress

21 Utility to reclamation Additional nursery management techniques* Aspen seedlings grown outside or in a greenhouse Shoot growth inhibitors Shortening of the photoperiod Nutrient reduction Withholding of water Supplementary CO 2 Particularly near the end of the growing season *Way et al. 2007; Sala et al. 2010; Landhäusser et al. 2012

22 Acknowledgements Shannon Hankin and Jake Gaster for field and laboratory assistance Cameron Stevenson at Crop Development Centre (CDC) North for logistical and research support Government, university and industry sponsors:

23 Questions?

24 References Landhäusser, S.M., B.D. Pinno, V.J. Lieffers and P.S. Chow 2012a. Partitioning of carbon allocation to reserves or growth determines future performance of aspen seedlings. Forest Ecology and Management 275: Landhäusser, S.M., J. Rodriguez-Alvarez, E.H. Marenholtz and V.J. Lieffers 2012b. Effect of stock type characteristics on field performance of aspen (Populus tremuloides Michx.) seedlings on boreal reclamation sites. New Forests 43: Sala, A., F. Piper and G. Hoch Physiological mechanisms of droughtinduced tree mortality are far from being resolved. New Phytologist 186: Way, D.A., S.D. Seegobin and R.F. Sage The effect of carbon and nutrient loading during nursery culture on the growth of black spruce seedlings: a six-year field study. New Forests 34: