Effects of Root Severance by Excavation on Growth, Physiology and Uprooting Resistance of Two Urban Tree Species

This experiment was carried out to evaluate the early physiological and growth response of two shade trees to root damage. European limes (Tilia × europea) and horse chestnuts (Aesculus hippocastanum) were planted in March 2004 and allowed to establish undisturbed for 5 years. In 2009, roots were damaged by either excavating one (MD) or two (SD) trenches at 40 cm from the root flare. Roots were excavated with an AirspadeTM to evaluate root loss caused by trenching. Shoot and diameter growth, leaf gas exchange, chlorophyll fluorescence and leaf water relations were determined up to 26 months after root severance. Results indicate that the growth reduction normally occurring after construction damage is due to reduced leaf gas exchange and less favorable water relations. Also, signs of photoinhibition were found in SD plants, particularly in horse chestnut. Therefore, root loss through trenching induced a mild water stress to severed trees, even in years characterized by high rainfall and water availability. More observations are needed to determine whether trees will be able to recover from damage or will decline further, especially if dryer years will occur before complete root regeneration.