1. Root Development in Soils

2. Root Growth Hypothesis—Minimum Effort
Note this is a generalized hypothesis, each species and soil combination responds differently. Nevertheless, if roots cannot penetrate soil layers, further soil development is limited.

3. Root Growth Hypothesis—Profile Rebuilding
Measure depth and root length density in situ
Frequent measurement can reveal root birth and death patterns (root turnover)
Soil genesis

4. Minimum Effort (a.k.a. Builder’s Special)
Four Treatments
Undisturbed
Minimum Effort (a.k.a. Builder’s Special)
Enhanced Topsoil
Profile Rebuilding
4 in (10 cm) topsoil
4 in (10 cm) topsoil, interface scuffed by tilling
Includes compost, subsoiling, and topsoil

5. Characterizing undisturbed soil
Shottower Silt Loam

6. Applying Compost: Profile Rebuilding

7. Preparing the plots: Pre Treatment
Vegetation and topsoil scraped and stockpiled
8 passes with a compactor at optimal moisture for compaction. Bulk density = 2.0 g/cm3

8. Tilling: “Enhanced Topsoil” and “Profile Rebuilding”
For the ET and PR treatments, the topsoil was rototilled to a depth of 8 inches (20 cm).
ET: to disrupt interface
PR: to prepare planting surface (eliminate clods)

9. Subsoiling Technique Step 1: Apply 4 inches leaf litter compost
Step 2: Use backhoe to go down 2 feet, scoop, and allow to fall down to break up clods. Large clods may require a prod with the backhoe. Creates veins of compost deep in profile.
Step 3: Apply 4 inches reserved topsoil
Step 4: Rototill to 8 inch depth
Similar to technique suggested by Kaj Rolf, Swedish researcher
Can be used in confined spaces (median strips, parking lot islands)
Addresses subsoil compaction

10. Plots in the fall after the first growing season
Plots in the fall after the first growing season. Accolade Elm on left grew extremely rapidly, nearly doubling in height.

11. Soil Preparation Affects Growth in First Year
Profile rebuilding essentially doubled tree growth in first year for elms and burr oaks. Smaller increases seen in other species. Increase in cross-sectional trunk area is an excellent measurement for integrating overall biomass increase.

13. Profile Rebuilding Short term Aids in establishment
We will be able to quantify how much canopy you get for your investment
To be determined in the long term
Soil biogenesis
Carbon storage
Root production and depth
Soil water capture

14. Questions to Pose
Can we improve soil function for stormwater throughout a city?
Can trees roots improve drainage from bioretention areas and make underdrainage unnecessary?

15. Partial support provided by the Tree Research & Education Fund