Effect of pervious and impervious pavement on the rhizosphere of American Sweetgum (Liquidambar styraciflua)

Mature trees help to offset urban area problems caused by impervious pavement. Trees in paved areas remain unhealthy due to a poor root zone environment. The objective of this experiment was to test if soil under pervious concrete, with greater water and gas infiltration, would be more beneficial to existing mature trees during urban development. Root activity, root growth and soil chemistry of American sweetgum under standard concrete, pervious concrete and no concrete were measured. Soil CO2 efflux rates and soil CO2 concentrations were extremely high under both concrete treatments. Soil under standard concrete had lower oxygen concentrations than soil under pervious concrete and control treatments, particularly under wet conditions. There was no pavement effect on soil water content or soil chemistry. Under control treatment standing live root length was greater than under both concrete treatments. There were no major differences in soil conditions between impervious and pervious concrete treatments. The soil under the plots, a Ships clay, with very low permeability may have prevented soil water infiltration. Likely this overrode any potential treatment effects due to porosity of the concrete. To obtain root zone benefits out of pervious concrete, a different base soil with a higher permeability would be a better alternative.