Root growth potential, water relations and carbohydrate status of ash alternative species following pre-plant storage

Abstract

The catastrophic loss of ash (Fraxinus spp.) trees in the midwestern United States due to emerald ash borer has emphasized the need for greater diversity in urban and community forests. However, the availability of some important Fraxinus alternative species may be limited due to difficulties in nursery production. We conducted two trials to examine growth and physiological responses of bare-root tree liners to pre-plant storage and handling. In both trials, bare-root liners were given one of four treatments for three weeks prior to planting: 1) control, 2) cold storage (4°C), 3) sweating (warm, moist storage), or 4) heeled-in (outdoor storage). Subjecting trees to a warm, moist environment before planting (sweating) increased shoot dieback of Celtic occidentalis trees. Root growth potential was very low for Quercus spp. trees and varied by treatment for Celtis occidentalis trees. Taxodium distichum trees had a relatively high root growth potential in all treatments. Stem water potential measured immediately before and after pre-plant treatments indicated that Quercus spp. trees and T. distichum trees were able to rehydrate during sweating while water stress in C. occidentalis trees remained high (stem water potential <−2.0MPa). The results suggest that poor transplanting success reported for Quercus spp. trees may be related to low root growth potential, whereas poor establishment of Celtis occidentalis trees is related to a combination of factors including desiccation, poor root regeneration and poor carbohydrate status. None of the pre-plant treatments reduced shoot dieback compared to control trees that were not stored prior to planting.