Growth response and adaptability of Acer rubrum and Acer x freemanii cultivars to soil compaction

Numerous research projects have investigated the tolerance of Acer spp. to flooding and drought. A major objective of the current study was to assess the growth response and adaptability of cultivars of A. rubrum and A. xfreemanii to soil compaction---a commonly cited problem in landscapes and nursery production.; Both field and greenhouse experiments were used to evaluate the effects of soil compaction on the trees. In the field, soil was compacted in a randomized block design in 2001 prior to planting and again in selected plots in 2002. Trees were fertilized at either 101.0 g L-1 or 25.3 g L-1 nitrogen fertilizer prior to planting in the field in October 2001 in a split-plot design. Soil and growth parameters were measured over a 3-year period. Soil compaction significantly increased bulk density, reducing total porosity, void ratio and saturated hydraulic conductivity.; Trees growing in compacted plots showed a significant decrease in some, but not all of the biomass measures throughout the study period. Cultivar type had a consistently significant effect on tree growth.; Acer xfreemanii Celebration(TM) outperformed all other cultivars when grown under any soil treatment. These affects may be due to a reduction in soil or plant hydraulic conductivity.; Trees treated with 101.0 g L-1 nitrogen showed significantly larger values for most growth parameters as compared to the trees treated with 25.3 g L-1 nitrogen. However, the trees receiving the higher fertilizer rate did not show greater adaptability to compacted soils.; Various greenhouse experiments attempted to mimic field conditions. PVC pipe pots served as intact lysimeters and trees were grown in these over a number of years. Growth parameters and soil conditions were measured over a 3-year period. Again, as bulk density increased total porosity, void ratio and saturated hydraulic conductivity were significantly decreased. In most years, transpiration was significantly reduced as compaction increased. Stomatal conductance was also reduced with an increase in soil density.; Soil gas sampling indicated sufficient concentrations of O2 present in both low and high-compaction soil treatments. As in the field, cultivar treatment was highly significant. There were inconsistent responses for some tree growth parameters when evaluated across the various compaction treatments. Some cultivars were more adversely impacted by the compaction than were others.