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 Subsoil B, Subsoil C) Subsoil Subsoil B 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 Subsoil B, Subsoil C) Subsoil Subsoil B C C C OB OB OB OB
Peat Peat FFM FFM Coversoil Placement Depth (i.e. 10cm Peat, 30cm Peat, 10cm FFM, 20cm FFM) Subsoil Subsoil Subsoil Subsoil 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
A Coversoil 200 40 Peat FFM 150 Subsoil B B 30 Subsoil C B 100 C 20
50 10 Vertical Growth (cm) Growth Vertical Average Height(cm) 2016 Average 0 0 Peat FFM Subsoil Bm Subsoil C 2014 2015 2016 Coversoil Year
Peat FFM Subsoil Subsoil Subsoil Subsoil B C C C *Graphs show least-squared means and adjusted confidence intervals 200 40
150 30
100 20 Growth (cm) Growth 50 10 Nutrients 0 Vertical 0
Average 2016 Height (cm) Height 2016 Average Peat FFM Bm C 2014 2015 2016 Coversoil Year
▪ FFM had higher levels of P, NH & K 4 Higher P encouraged ▪ Peat had higher levels of NO3, 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
200 40 than coarse-textured soils 150 30 100 20 ▪ Increased water availability during 50 10 0 0 2016 Height (cm) Height 2016 Peat FFM Bm C 2014 2015 2016 dry growing season
Coversoil (cm) Growth Vertical Year
Wilting Point in Peat
Wilting Point in Sand Temperature ▪ Peat had highest organic content
200 40 ▪ Insulative effect likely decreased 150 30 100 20 temperature 50 10 0 0 2016 Height (cm) Height 2016 Peat FFM Bm C 2014 2015 2016 ▪ Higher water content also played role
Coversoil (cm) Growth Vertical Year 2015 Cover Soil Temperatures at 15cm Depth
25
C) ° ( 20
15 Cover Soil Peat FFM Subsoil Bm 10 Subsoil C
5 Daily Soil Temperature SoilTemperature Daily
05-15 06-15 07-15 08-15 09-15 10-15 Time (Month-Year) Impact of Coversoil Placement Depth
2016 Height Growth Treatment: p = 0.2 Treatment x Year: p = 0.01
200 Coversoil Depth Peat 10 Peat 30 40 150 FFM 10 FFM 20
100 20
50
Vertical Growth(cm) Vertical 0
0 Average (cm) Height 2016 Average Peat 10 Peat 30 FFM 10 FFM 20 2014 2015 2016 Coversoil Year Peat Peat FFM FFM
Subsoil Subsoil Subsoil Subsoil C C C C *Graphs show least-squared means and adjusted confidence intervals 200
150 ▪ Aspen growth in 10cm peat similar to the sandier
100 FFM coversoils
50 ▪ Less water held in 10cm peat and FFM coversoils
Average 2016 Height (cm) Height 2016 Average 0 Peat 10 Peat 30 FFM 10 FFM 20 Coversoil compared to 30cm of peat each year, especially during 2015 drought.
40 ▪ 10cm peat had cool seasonal soil temperatures 20 that were similar to the 30cm peat Vertical (cm) Growth Vertical 0 • However, 10cm peat had 4-10 more growing 2014 2015 2016 Year days with soil temperature above 5°C Peat Peat FFM FFM • May have supported early start to growth each 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 60 Treatment x Year: P = 0.2 A Subsoil 200 AB Bm BC B 40 150 C
100 20
50 Growth(cm) Vertical 0
Average (cm) Height 2016 Average 0 Bm BC C 2014 2015 2016 Subsoil Year
FFM FFM FFM Subsoil Bm Blended Subsoil Subsoil B/C C C *Graphs show least-squared means and adjusted confidence intervals 60 200 40 150
100 20
50 (cm) Growth Vertical Nutrients 0 0 Average 2016 Height (cm) Height 2016 Average Bm BC C 2014 2015 2016 Subsoil Year
▪ Subsoil Bm had highest levels of P Higher P ▪ All three subsoils had similar levels encouraged of N and K faster growth Water ▪ 1-3% less silt in the BC subsoil
60 200 ▪ Coarser textured soil held less water 40 150 100 20 and could not buffer against the 50 0 2015-2016 drought 0 (cm) Growth Vertical Bm BC C 2014 2015 2016 Average 2016 Height (cm) Height 2016 Average Subsoil Year Growing Season (May-Sept) Water Content at 15cm Depth 0.15
) 0.10 Subsoil
3 -
Bm cm
3 BC
(cm C 0.05 Wilting Point
in Sand Average Water Content Water Average
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.