Influence of nursery production system on water status in transplanted trees

Abstract

The objective of this study was to investigate the influence of the nursery production system on post-transplant water uptake and stress in urban trees during the establishment phase. Field-grown trees of sweet cherry (Prunus avium L) and red oak (Quercus rubra L) were either transplanted as bare-rooted or balled & burlapped, or subjected to fine-root-stimulating measures (in so called pre-establishing systems) as root-pruning, air-potting or fabric-container-cultivation in the nurseries one year prior to transplanting. All trees were planted at two sites: one occasionally dry site in the city of Malmö and one with adequate water supply at all times, at an experimental rural site at Alnarp campus, both in Sweden. Shoot water potential was determined every third week at midday and pre-dawn the following morning during the three first years after transplanting. Leaf surface area was measured annually. The red oak trees from the pre-establishing systems showed higher water potentials at every measuring occasion compared to that of bare-rooted red oak trees at the rural site during the first year. The air-potted sweet cherry trees at the rural site had higher midday water potential than the bare-rooted trees at every measuring occasion during the first year. Leaf surface area was larger for air-potted red oaks than bare-rooted red oaks during the first post-transplant year (p<0.001, both sites). The differences between the production systems did not persist during the following two years. Leaf surface area was restored to pre-transplant size in all trees at the rural site after three years but still reduced at the urban site. These results suggest that the pre-establishing systems do have an impact on water status when soil water availability is sufficient, but less significance in typically urban areas, with limited soil water during the initial post-transplant phase. The results indicate that red oak and sweet cherry trees planted in an urban context, with occasionally low soil water amounts, are not favored by cultivation in pre-establishing systems prior to transplant, and that low water availability cannot be compensated for by high amounts of fine roots. Good establishment management is required also for trees submitted to pre-establishing measures.