10 Arboriculture & Urban Forestry 2009. 35(1):10–13. Struve: Tree Establishment Tree Establishment: A Review of Some of the Factors Affecting Transplant Survival and Establishment Daniel K. Struve Abstract. Transplant success and tree establishment depend on a chain of events from propagation, to production, to harvest, to shipping, to maintenance on the job site, to transplanting techniques, to aftercare. Failure to follow proper practices at any step in this sequence will compromise transplant success and establishment. This article reviews some of the factors that induce transplant shock and slow establishment of transplanted nursery stock such as root and mineral nutrient loss, soil moisture stress and xylem vessel cavitation, and methods used to reduce transplant shock. Key Words. Biostimulants; establishment; root growth potential; transplanting. This article discusses some of the causes of transplant shock (root loss, root system morphology, phenology of shoot and root devel- opment, and soil moisture stress), the measures of establishment, the benefits of biostimulants, and the effect of tree caliper on red oak establishment. This review is not comprehensive; it uses examples from the author’s research with red oak ( Quercus rubra L.), which is considered a coarse-rooted species and relatively difficult to transplant. Also, the earlier citations that demonstrate a principle are given for a historical perspective, with apologies to authors of more recent citations. Transplant Shock Transplant shock is a condition of distress from injuries, deple- tion, and impaired functions; a process of recovery; and a period of adaptation to a new environment (Rietveld 1989). Transplant shock is initiated by root system loss resulting from either bare root or balled-and-burlapped harvest (Watson and Sydnor 1987). Root loss reduces the tree’s ability to absorb water and mineral nutrients and causes the loss of storage compounds such as car- bohydrates and mineral nutrients. For instance, up to 50% of a 1-year-old red oak ( Quercus rubra L.) root system is storage car- bohydrate (Larson 1978). By late September, the root system of a 1-year-old red oak seedling contains up to 60% of the seedlings total nitrogen (Larimer and Struve 2002) and an estimated 80% of seedling’s nitrogen content after defoliation. When dormant deciduous plant material is transplanted, trans- plant shock severity is also related to the relative timing between the initiation of shoot growth and first root regeneration. Under benign greenhouse conditions, shoot growth in transplanted (root pruned) red oak seedlings preceded first root regeneration by as many as 33 days (Johnson et al. 1984). Transplanted red oak seedlings adjusted to transplant-induced water stress by reducing leaf area thereby maintaining net assimilation, conductance, and transpiration (on a cm 2 leaf surface area basis) similar to that of untransplanted seed- lings (Struve and Joly 1992). However, because of significantly reduced leaf surface area of transplanted seedlings (1.8 to 2.4 times less leaf area), estimated whole plant transpiration and net assimila- tion rates are higher in untransplanted seedlings. For species with fibrous root systems, the delay between budbreak and first root ©2009 International Society of Arboriculture regeneration is less because first root regeneration occurs through elongation of existing root tips and not from adventitious root regen- eration (Arnold and Struve 1989). There are two types of root regeneration: elongation of existing root tips and initiation of adventitious roots and their subsequent elongation (Stone and Shubert 1959). Initial seedling survival is dependent on the elongation of existing roots, which is indepen- dent of the season of the year and occurs whenever soil moisture and temperatures permit. Establishment is dependent on initia- tion and elongation of new roots, which is confined primarily to late winter and early spring, even when nonlimiting soil moisture and temperatures are provided. Thus, fibrous-rooted species are easier to transplant then coarse-rooted species because they have higher root regeneration potential resulting from greater num- bers of rapidly regenerating intact root tips at harvest. In con- trast, coarse-rooted species have few intact root tips after harvest. Thus, root regeneration results from new root initiation and sub- sequent elongation. Root regeneration potential is significantly reduced by even moderate (–0.4 MPa) soil moisture stress (Larson and Whitmore 1970 ). Soil moisture stress also reduces root elongation. Root elongation is also inhibited in compacted soils and the root growth inhibition made worse by the combination of soil compaction and low soil moisture content (Bennie 1991). Another physiological factor affecting spring-transplanted nursery stock in temperate regions is xylem dysfunction, espe- cially for ring porous species such as Quercus . For red oak, there is a 20% loss of hydraulic conductivity in current-season shoots as a result of cavitation by August (Cochard and Tyree 1990). After the first hard frost, cavitation is greater than 90%. Thus, red oak must form new xylem in spring to restore hydraulic con- ductivity. It seems likely that rough handling of nursery stock in early spring would damage the developing xylem and com- promise hydraulic conductivity and, consequently, survival and establishment. Also, summer digging of oaks would result in cav- itation of large xylem vessels and would compromise survival. Defuse porous species are less susceptible to cavitation than ring- porous species (Cochard and Tyree 1990) and, by inference, suf- fer less cavitation when handled roughly or summer dug than ring-porous species.
January 2009
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