Characterization of Physical, Gaseous, and Hydrologic
Properties of Compacted Subsoil and its Effects on
Growth and Transpiration of Two Maples Grown
Under Greenhouse Conditions
Barbara A. Fair, James D. Metzger, and James Vent
Abstract: City foresters and horticulturists often seek trees suited for urban conditions. Two maples often used were selected to assess response to compacted soil: ‘Armstrong’ Freeman maple and ‘Brandywine’ red maple. Soil physical parameters were assessed to determine effects of high density on movement of gas and water. Rigid-walled lysimeters constructed from polyvinyl chloride pipe were filled with clay subsoil compacted to 1.64 g·cm-3 (MODERATE-density) and 1.78 g·cm-3 (HIGH-density). Compaction decreased total porosity and saturated hydraulic conductivity. In addition, CO2 concentrations in compacted soil were 5–18 times higher than atmospheric concentrations, while O2 concentrations were similar to atmospheric levels despite density. O2 concentration played no real role in plant growth response to compaction. Trees growing in MODERATE-density soils had higher transpiration rates than trees growing in HIGH-density soils, although differences decreased over time. A high soil density did not affect caliper growth, but did reduce annual height growth, leaf area and dry weight, and stem dry weight, but responses varied over time and between species. Root dry weight and volume were unaffected by compaction, but root:shoot ratio was higher for trees growing in HIGH-density soils, which is expected as aboveground biomass is typically reduced by soil compaction.
Keywords: Acer × freemanii ‘Armstrong’; Acer rubrum ‘Brandywine’; Bulk Density; Lysimeter; Saturated Hydraulic Conductivity; Soil Compaction;
Transpiration; Urban Forestry.