Urban tree establishment
Sammanfattning: The aim of this PhD project was to study tree establishment, both how it may be improved in urban areas and how it is measured and defined. The establishment phase of trees is a period of reduced tree vitality, and a successful establishment is crucial for long-term survival and prosperity of newly planted trees. However, failed plantings and poor establishment is a common problem in the often harsh growing conditions present in urban areas. Improving tree establishment is thus important for securing the presence of trees in urban environments. Another important part is to understand how the process of establishment is expressed in trees, so that the needs of the trees can be met. Tree nursery industry has recently developed production systems that aim to produce trees that are better prepared for transplanting. This study set out to investigate the effect nursery production systems might have on tree establishment success, and to examine different ways of assessing establishment, since the term is not consistently defined. Sweet cheery and red oak trees, cultivated as either bare-rooted (BR), balled & burlapped (B&B), root-pruned (RP), air-potted (AP) or fabric container (FC) grown were planted at one urban and one rural site in Southern Sweden. The trees were studied during the final nursery year and the four first post-transplant years. The production systems influenced total root length for both species, providing root systems with large differences in appearance. Shoot growth was restored to pre-transplant values for RP, FC and B&B sweet cherry trees at the rural site, three years after transplanting. Water status was significantly higher for AP trees than BR trees of both species, but only during the first year after transplanting, at the rural site. In general, effects of production system were more pronounced at the rural site with the higher water availability, indicating that none of the studied production systems was superior to use in urban plantings. Visual assessments of the establishment success of the trees were affected by leaf size, colour and shape. Leaf size was related to water status. Water status and shoot growth measurements were not correlated during the first years after transplanting. The term establishment can be used in different ways, and the differences might affect the outcome of an establishment assessment.
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