Tree Growth and Gas Exchange Response of Ficus benjamina ‘Evergreen’ Cultivated in Compacted and Remediated Urban Soils Under Water Deficit Conditions

Abstract

Trees growing in the urban environment are often subject to a variety of edaphic stressors that can lead to premature decline. As a result, soil restoration methods are required. The scoop and dump (S&D) technique of soil remediation is the practice of incorporating large volumes of organic matter (33% v/v) into the soil profile. A controlled greenhouse experiment was conducted to determine if S&D soils affected growth of Weeping Fig (Ficus benjamina ‘Evergreen’) trees during establishment (fourteen weeks) and gas exchange during a twenty-six-day water deficit period. S&D soils displayed decreased mean bulk density, increased accumulative gravimetric water holding capacity, and increased mean organic matter compared to unamended soils. In the remediated soils, Ficus benjamina ‘Evergreen’ showed a significant increase in the growth of roots, shoots, and leaf area. The increased leaf area of trees in the S&D soils caused greater transpiration on a whole-plant basis. As a result, the increased water-holding capacity in S&D soils were utilized at a statistically equal rate as the trees in unamended soils. Trees growing in both soil treatments displayed statistically equal reductions in gas exchange during the water deficit period. This study finds that urban soils treated with the S&D technique significantly reduces root-limiting compaction and increases tree biomass growth.