Challenges in Reconstructing Soils: Building the Foundation for Forest Restoration in Mine Reclamation Sites Shauna Stack, Caren Jones, Jana Bockstette and Simon Landhäusser CLRA/ACRSD 2018 National Conference and AGM University of Alberta, Department of Renewable Resources, Edmonton, AB
Boreal Mixedwood Subregion
Upland Native trees planted in Reclamation reconstructed soils Reconstructed soils used as capping material Man-made upland features (i.e. lean oil sand overburden)
The Aurora Soil Capping Study • Trees were planted in 2012 and their heights were measured each year until 2016 (i.e. 5 years) • Density of 10,000 stems per hectare Measured over the same time period: ▪ Soil nutrients at time of placement ▪ Soil water content ▪ Soil temperature ▪ Precipitation
Research Questions How do the following reconstructed soils impact the growth of Trembling Aspen in upland reclamation? Peat FFM Coversoil Type (i.e. Peat, Forest Floor Material, Subsoil Subsoil C Subsoil B Subsoil Subsoil B, Subsoil C) C C OB OB OB OB Peat FFM Subsoil B Subsoil C
Research Questions How do the following reconstructed soils impact the growth of Trembling Aspen in upland reclamation? Peat FFM Coversoil Type (i.e. Peat, Forest Floor Material, Subsoil Subsoil C Subsoil B Subsoil Subsoil B, Subsoil C) C C OB OB OB OB Peat FFM Peat FFM Coversoil Placement Depth (i.e. 10cm Peat, 30cm Peat, Subsoil Subsoil Subsoil Subsoil 10cm FFM, 20cm FFM) C C C C OB OB OB OB FFM FFM FFM Subsoil Bm Underlying Subsoil Type (i.e. Subsoils Bm, BC and C) Blended Subsoil Subsoil B/C C C OB OB OB
Impact of Coversoil Type 2016 Height Growth Treatment: p = 0.004 Treatment x Year: p < 0.001 Average 2016 Height (cm) Coversoil A 200 40 Peat Vertical Growth (cm) FFM Subsoil B 150 30 Subsoil C B B 100 20 C 50 10 0 0 2014 2015 2016 Peat FFM Subsoil Bm Subsoil C Year Coversoil Peat FFM Subsoil Subsoil Subsoil Subsoil B C C C *Graphs show least-squared means and adjusted confidence intervals
Average 2016 Height (cm) 200 40 Vertical Growth (cm) 150 30 Nutrients 100 20 50 10 0 0 Bm 2014 2015 2016 Peat FFM C Year Coversoil ▪ FFM had higher levels of P, NH 4 & K Higher P encouraged ▪ Peat had higher levels of NO 3, S & K faster growth in ▪ Subsoils had lower levels of N, P and aspen K compared to FFM and Peat
Water ▪ Organic matter held more water than coarse-textured soils Vertical Growth (cm) 2016 Height (cm) 200 40 150 ▪ 30 Increased water availability during 100 20 50 10 dry growing season 0 0 2014 2016 Peat FFM Bm C 2015 Coversoil Year Wilting Point in Peat Wilting Point in Sand
Temperature ▪ Peat had highest organic content ▪ Insulative effect likely decreased Vertical Growth (cm) 2016 Height (cm) 200 40 150 30 temperature 100 20 50 10 ▪ Higher water content also played role 0 0 2014 2016 Peat FFM Bm C 2015 Coversoil Year 2015 Cover Soil Temperatures at 15cm Depth 25 Daily Soil Temperature (° C) 20 Cover Soil 15 Peat FFM Subsoil Bm 10 Subsoil C 5 05-15 06-15 07-15 08-15 09-15 10-15 Time (Month-Year)
Impact of Coversoil Placement Depth Growth 2016 Height Treatment x Year: p = 0.01 Treatment: p = 0.2 Coversoil Depth 200 Average 2016 Height (cm) Peat 10 Vertical Growth (cm) Peat 30 40 FFM 10 150 FFM 20 100 20 50 0 0 2014 2015 2016 Peat 10 Peat 30 FFM 10 FFM 20 Year Coversoil Peat FFM FFM Peat Subsoil Subsoil Subsoil Subsoil *Graphs show least-squared means C C C C and adjusted confidence intervals
200 Aspen growth in 10cm peat similar to the sandier ▪ Average 2016 Height (cm) 150 FFM coversoils 100 50 Less water held in 10cm peat and FFM coversoils ▪ 0 compared to 30cm of peat each year, especially Peat 10 Peat 30 FFM 10 FFM 20 Coversoil during 2015 drought. 40 Vertical Growth (cm) 10cm peat had cool seasonal soil temperatures ▪ 20 that were similar to the 30cm peat However, 10cm peat had 4-10 more growing • 0 days with soil temperature above 5 ° C 2014 2015 2016 Year • May have supported early start to growth each Peat FFM FFM Peat spring compared to the cooler 30cm of peat Subsoil Subsoil Subsoil Subsoil C C C C OB OB OB OB
Impact of Subsoil Type 2016 Height Growth Treatment: p = 0.1 Treatment x Year: P = 0.2 60 A Vertical Growth (cm) Subsoil Average 2016 Height (cm) 200 AB Bm BC 40 B C 150 100 20 50 0 0 Bm BC C 2014 2015 2016 Year Subsoil FFM FFM FFM Subsoil Bm Blended Subsoil Subsoil B/C C *Graphs show least-squared means C and adjusted confidence intervals
60 Vertical Growth (cm) Average 2016 Height (cm) 200 40 150 Nutrients 100 20 50 0 0 Bm BC C 2014 2015 2016 Year Subsoil ▪ Subsoil Bm had highest levels of P Higher P encouraged ▪ All three subsoils had similar levels faster growth of N and K
Water ▪ 1-3% less silt in the BC subsoil Average 2016 Height (cm) ▪ Coarser textured soil held less water 60 Vertical Growth (cm) 200 40 and could not buffer against the 150 100 20 50 2015-2016 drought 0 0 Bm BC C 2014 2015 2016 Subsoil Year Growing Season (May-Sept) Water Content at 15cm Depth 0.15 Average Water Content 0.10 Subsoil (cm 3 cm -3 ) Bm BC C 0.05 Wilting Point in Sand 0.00 2013 2014 2015 2016 Year
Conclusion ▪ Higher P levels in upland forest floor material support greater tree growth ▪ Organic-rich soils such as peat held more water than coarser cover soils and buffered against dry growing conditions. However, soil temperature limitations may require consideration when organic • content is high and the material is placed in thick layers at the surface. ▪ Small amounts of silt can greatly improve the water holding ability of coarse textured subsoils. Higher P availability in these subsoils can also improve nutrient conditions as • tree roots expand in the rooting medium.
Acknowledgements Thank you to the members of the Landhäusser Research Group (Fran Leishman, Caren Jones, Pak Chow, Jana Bockstette, Erika Valek, Ashley Hart, Natalie Scott, Kevin Solarik, Morgane Merlin, Erin Wiley and our fantastic summer students) as well as Syncrude Canada Ltd for their help and data support.
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