Foundation for Forest Restoration in Mine Reclamation Sites Shauna - - PowerPoint PPT Presentation

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 Reclamation

Native trees planted in 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?

Coversoil Type (i.e. Peat, Forest Floor Material, Subsoil B, Subsoil C)

Peat Subsoil C OB FFM Subsoil C OB Subsoil B OB Subsoil C OB

Peat FFM Subsoil B Subsoil C

Research Questions

How do the following reconstructed soils impact the growth of Trembling Aspen in upland reclamation?

Subsoil Bm Subsoil C FFM OB Subsoil C FFM OB Blended B/C FFM OB

Underlying Subsoil Type (i.e. Subsoils Bm, BC and C) Coversoil Type (i.e. Peat, Forest Floor Material, Subsoil B, Subsoil C)

Peat Subsoil C OB FFM Subsoil C OB Subsoil B OB Subsoil C OB Peat Subsoil C OB Peat Subsoil C OB FFM Subsoil C OB FFM Subsoil C OB

Coversoil Placement Depth (i.e. 10cm Peat, 30cm Peat, 10cm FFM, 20cm FFM)

Impact of Coversoil Type

Peat Subsoil C FFM Subsoil C Subsoil B Subsoil C

A B 50 100 150 200 Peat FFM Subsoil Bm Subsoil C Coversoil Average 2016 Height (cm) B C 2016 Height Treatment: p = 0.004 10 20 30 40 2014 2015 2016 Year Vertical Growth (cm) Growth Treatment x Year: p < 0.001 Coversoil Peat FFM Subsoil B Subsoil C

*Graphs show least-squared means and adjusted confidence intervals

▪ FFM had higher levels of P, NH4 & K ▪ Peat had higher levels of NO3, S & K ▪ Subsoils had lower levels of N, P and K compared to FFM and Peat

Higher P encouraged faster growth in aspen

Nutrients

50 100 150 200 Peat FFM Bm C Coversoil Average 2016 Height (cm) 10 20 30 40 2014 2015 2016 Year Vertical Growth (cm)

Water

Wilting Point in Peat Wilting Point in Sand

▪ Organic matter held more water than coarse-textured soils ▪ Increased water availability during dry growing season

50 100 150 200 Peat FFM Bm C Coversoil 2016 Height (cm) 10 20 30 40 2014 2015 2016 Year Vertical Growth (cm)

5 10 15 20 25 05-15 06-15 07-15 08-15 09-15 10-15 Time (Month-Year) Daily Soil Temperature (° C) Cover Soil

Peat Subsoil Bm Subsoil C FFM

2015 Cover Soil Temperatures at 15cm Depth

▪ Peat had highest organic content ▪ Insulative effect likely decreased temperature ▪ Higher water content also played role

Temperature

50 100 150 200 Peat FFM Bm C Coversoil 2016 Height (cm) 10 20 30 40 2014 2015 2016 Year Vertical Growth (cm)

Impact of Coversoil Placement Depth

Peat Subsoil C Peat Subsoil C FFM Subsoil C FFM Subsoil C

50 100 150 200 Peat 10 Peat 30 FFM 10 FFM 20 Coversoil Average 2016 Height (cm) 2016 Height Treatment: p = 0.2 Growth Treatment x Year: p = 0.01 20 40 2014 2015 2016 Year Vertical Growth (cm) Coversoil Depth Peat 10 Peat 30 FFM 10 FFM 20

*Graphs show least-squared means and adjusted confidence intervals

Peat Subsoil C OB Peat Subsoil C OB FFM Subsoil C OB FFM Subsoil C OB

▪ Aspen growth in 10cm peat similar to the sandier FFM coversoils ▪ Less water held in 10cm peat and FFM coversoils compared to 30cm of peat each year, especially during 2015 drought. ▪ 10cm peat had cool seasonal soil temperatures that were similar to the 30cm peat

• However, 10cm peat had 4-10 more growing

days with soil temperature above 5°C

• May have supported early start to growth each

spring compared to the cooler 30cm of peat

50 100 150 200 Peat 10 Peat 30 FFM 10 FFM 20 Coversoil Average 2016 Height (cm) 20 40 2014 2015 2016 Year Vertical Growth (cm)

Impact of Subsoil Type

Subsoil Bm Subsoil C FFM Subsoil C FFM Blended B/C FFM *Graphs show least-squared means and adjusted confidence intervals

20 40 60 2014 2015 2016 Year Vertical Growth (cm) Growth Treatment x Year: P = 0.2 Subsoil C BC Bm 50 100 150 200 Bm BC C Subsoil Average 2016 Height (cm) A B AB 2016 Height Treatment: p = 0.1

▪ Subsoil Bm had highest levels of P ▪ All three subsoils had similar levels

• f N and K

Higher P encouraged faster growth

Nutrients

20 40 60 2014 2015 2016 Year Vertical Growth (cm) 50 100 150 200 Bm BC C Subsoil Average 2016 Height (cm)

0.00 0.05 0.10 0.15 2013 2014 2015 2016 Year Average Water Content (cm3 cm-3) Subsoil Bm BC C

Growing Season (May-Sept) Water Content at 15cm Depth

Wilting Point in Sand

Water

▪ 1-3% less silt in the BC subsoil ▪ Coarser textured soil held less water and could not buffer against the 2015-2016 drought

20 40 60

2014

2015

2016

Year Vertical Growth (cm) 50

100 150 200

Bm BC C Subsoil Average 2016 Height (cm)

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.