Forest Road Restoration:

Transcription

1 David H McNabb PhD, RPF ForestSoil Science Ltd. Edmonton, Alberta Forest Road Restoration: The Challenge of Changing Expectations February

2 Challenges - Time No longer just an issue of wood supply Fragmentation of the landscape Restore desired forest cover quickly Erect physical barriers Integrate restoration practices with other harvesting and silvicultural operations Effective and efficient Do it once with confidence To borrow a quote from Mike Holmes Do it Right Remove the road footprint Do it permanently

3 Challenges - Time What we do may initially be effective.

4 Challenges - Time What we do has to be effective for the long term - after 20 years (right)

5 Challenges - Time The challenge is minimizing forest fragmentation If we don`t do it now, when will we do it?

6 Challenges - Time The world can now see how well we do Google Earth automated mapping of Alberta in-block roads

7 Challenges Road Impacts Temporary Roads are compacted are compacted to maximum soil density (McNabb For. Ecol. Mngt. 66: ) Impact on hydrologic function can exceed 50cm in depth (impacts pore sizes) Three sizes of soil pores: - Macropores (largest): Filled with air at field capacity (-15kPa) - Mesopores (medium): Filled with water for plant use (lowest -1500kPas) - Micropores (smallest): Water is not accessible

8 Challenges Road Impacts / Time Natural recovery processes: Biological roots & biota Freeze/thaw Surface soil process Horizontal layering Medium textured soils Most benefit in 1-3 cycles Snow insulates soil Shrink/swell Smectitic clays

9 Challenges Road Impacts / Time Road impacts to soil are essentially permanent Subsoils in old roads remain compacted for 100+ years Assuming that natural recovery of subsoil will occur is wishful thinking Impacts on hydrologic function difficult to measure. (Schjonning et al SSSAJ 77: )

10 Challenges Road Impacts: Compaction versus Massive Soil Level of Soil Wetness and Severity of Trafficking Compaction moderate soil wetness and high impact Massive Soil soil wetness limits compaction but destroys soil structure Common denominator is a change in pore size distribution and loss of soil structure starting with the macropore space Common consequence is hydrologic function of a trafficked soil is impaired

11 Challenges - Impaired Hydrologic Function of Soils Vadose Zone Definition - The aerated region of soil above the permanent water table H 2 O Restrictive soil layers affect the hydrologic function of soil Soil aeration Drainage class Drought issues Restrictive Soil Horizon

12 Challenge Sustainable Forests Needs Soil What is the most important soil component? Quantity and quality of soil Deep, medium textured, no restrictions Example: white spruce windthrow NE Peace River Common perception of forests: Most of the roots are near the surface Effective rooting depth is shallow 80+ percent of roots are in the top 20 cm Review of tree root distribution(stone and Kalisz, 1991) How deep soils dry is the most important measure of the soil volume Restrictive soil layers are a major cause of shallow root penetrations

13 Challenge Restoring soil #1: quantity and quality Dozer Rippers Tools of Convenience Critical Depth limits effectiveness of rippers and other tinges. Loosened Soil Critical Depth Shank

14 Challenge Rippers and Conventional Tillage Are Ineffective Non-conventional tillage of summer haul road

15 A New Tillage Option? Why was rough tillage effective? Because it maximizes the effectiveness of freeze/ thaw process in several ways: Increases the melting of snow in early fall Increases soil wetness Increases depth and rate of frost penetration Allows lateral expansion of soil during freezing in addition to the normal vertical only expansion

16 A New Tillage Option? What about soil quality? Forest Floor Organics and Topsoil are an important component of the original soil quality Original Alberta study of plowing and topsoil spreading Lodgepole pine after 18 years Plow + Topsoil Encouraged the understory Plow only Mixing/homogenizing soil layers reduces tillage benefit (Krzic et al. 2009)

17 Proposed Solution: An Ecological Approach to Soil Restoration Soils are evolving and changing over time Source: : Why soil science must embrace an ecosystems approach (Robinson et al. 2012) Historically, we have tried to rebuild soil to look like the original. What if we take an ecosystems approach to soil restoration?? Retain key components Restart soil development Disturbance based

18 Principles for the Ecological Restoration of Soil Retain topsoil and fine debris Deep tillage is required, 70+ cm Minimize mixing of soil layers Till soil in no more than two passes Leave soil rough and porous Maximize potential for freeze/thaw process Last step don t traffic soil again RipPlow on Cat D7R Desired Outcome: Effective tillage increases soil elevation Video: How to use a RipPlow in forest reclamation

19 Long-term Benefits of Effective Deep Tillage Soil elevation increases an average of 15 cm. After 4 years, increase in elevation remains about 4-5 cm. Lowers water table Improves soil aeration Increases soil water storage Agricultural benefits of effective deep tillage can be long lasting. Without trafficking, benefits of deep tillage in forests, should persist for a long time. Ecologically: Restoring hydrologic function, Resetting soil development processes that are appropriate for the site. Second Pass First Pass

20 Forest Road Restoration Excavator and Dozer

21 Forest Road Restoration Excavator RipPlow Hitachi 200 with RipPlow and thumb Trench training up to 5 m reach

22 Ecological Restored Soil Old badly reclaimed wellsite Plowed but poor veg control Planted white spruce at year-5 Aerial imagery at year-9 Poplar cutting 15 cm long (left) planted on plowed forest road at year-3.

23 Successful yet? Full potential of effective soil restoration requires adherence to established reforestation principles. Deep tillage and microsite management High quality planting stock delivered to the planting hole High quality microsite selection and planting technique Timely Longterm: Ecological soil restoration should allow roads to regenerate similar to the surrounding stand in the event of a wildfire.

24 Acknowledgements, etc. Alberta Environmental Centre, Vegreville later Alberta Research Council Weyerhaeuser (Edson Alberta Division) Reforestation plow and pullback trial (photo at left) Logging road soil impact study Weyerhaeuser (Alberta operations), Burlington Resources/ConocoPhillips, and Alberta Forest Research Institute Testing of deep tillage implements and development of best management practices for restoring soil on old and newly reclaimed wellsites Alberta Forest Industries Integration of excavators and dozer RipPlows for forest road restoration Contact: David H. McNabb, PhD, RPF ForestSoil Science Ltd Strathearn Crescent NW Edmonton, Alberta T6C4C5 Phone: (780) Fax: (780) Cell: (780) RipPlows for dozers and excavators are manufactured by ForestSoil Science Ltd, Edmonton, Alberta Canada Patent: 2,586,933 United States Patent: 8,176,993 B2