Arboriculture & Urban Forestry 39(5): September 2013 205 Table 1. Mean annual shoot growth of the five production methods for sweet cherry trees and red oak trees, including both Malmö and Alnarp sites. Year B&B RP AP FC P-values Sweet cherry 2007 41.6a 42.6a 9.9b 2008 3.6c 42.2a 10.8b 6.1bc 6.0bc 13.6a 9.6ab <0.0001 0.0002 2009 9.6a 6.2ab 4.8ab 5.0ab 4.1b 0.0253 2010 16.0c 23.1abc 31.6ab 20.4bc 35.1a 0.0010 2011 18.9b 19.6ab 24.0ab 19.3ab 27.5a 0.0200 Red oak 2007 50.0a 54.8a 34.3b 18.9c 15.8c 2008 8.3bc 15.0a 4.2c 2009 6.6ab 5.9ab 3.7b 2010 11.2ab 8.2bc <0.0001 <0.0001 10.2a 4.5b 0.0177 5.96ab 4.9ab 3.7b 6.6a 5.2ab 0.0373 2011 Stage in trial Pre-transp. Post-transp1 Post-transp2 Post-transp3 Post-transp4 Pre-transp. Post-transp1 Post-transp2 Post-transp3 Post-transp4 BR 10.8a 11.7a 8.7a 10.4a 10.4a 0.8767 Note: BR – bare-rooted, B&B – balled and burlapped, RP – root-pruned, AP – air-potted, FC – fabric container. Means within a column are based on 10 trees’ shoot growth. Different letter indicates significant differences at 0.05 level using Tukey’s test. Table 2. Mean accumulated shoot growth of sweet cherry and red oak, including and excluding the nursery year (2008), in Malmö and Alnarp sites. Treatment BR B&B RP AP FC P-values Sweet cherry 2007–2011 Malmö Red oak Alnarp 72.9 ± 13.1ab 101.8 ± 9.3 81.5 ± 16.9a 50.3 ± 23.9b 84.8 ± 14.2a 0.640 2008–2011 Malmö Alnarp 2007–2011 Malmö 113.7 ± 24.8 39.0 ± 16.7 71.0 ± 24.6a 86.0 ± 8.6a 106.6 ± 10.4 42.9 ± 22.1 89.5 ± 7.3a 116.3 ± 23.3 41.8 ± 11 71.7 ± 14.1ab 102.6 ± 23.6 59.8 ± 18.6 92.9 ± 24a 0.029 0.193 0.035 with the higher accumulated post-transplant shoot growth dif- fered between the two sites. AP trees showed the highest accumulated shoot growth at Alnarp and B&B trees in Malmö. Root Systems The production methods appeared to have considerable effects on the visual appearance of the root systems (Figure 2). All roots investigated had relatively shallow root systems with roots in all directions. The root systems within each species appeared to have the same amount of first-and second-order lateral roots. For FC grown trees, these roots were more shortened due to the root pruning that took place before the trees were installed in the fab- ric containers. Both species grown with the AP and FC methods responded vigorously, producing root systems that gave an impression of a high density of small-diameter roots. The FC root systems appeared very compact, and the small-diameter roots were evenly spread throughout the fabric container. The majority of the small-diameter roots of the AP root systems were found in the outer part of the root ball, where the peat had been located. The root systems of B&B and BR trees had small amounts of small- diameter roots. B&B root systems were more compact than BR root systems. The two species reacted differently to root pruning, which seemed to stimulate the growth of small-diameter roots in sweet cherry trees, whereas the effect was much less in red oak. The root system of RP red oak trees was not visually different from that of the B&B trees, but a difference was seen between sweet cherry trees produced with these two methods. RP sweet cherry trees appeared to have the densest root system of all the sweet cherry trees, with small-diameter roots throughout the root ball. WinRHIZO scanning (Figure 3) showed that sweet cher- ry trees had almost twice the number of small-diameter roots of red oak. The scannings also showed that there were great variations in total fine-root length between the production 47.8 ± 5.9b Alnarp 2008–2011 Malmö 28.7 ± 3.5a 12.4 ± 2.6b 20.8 ± 7ab 0.025 Alnarp 33.9 ± 12.7 62.4 ± 10.1a 70.0 ± 10.3a 89.5 ± 12.2ab 22.7 ± 2.8ab 36.3 ± 14.6ab 97.1 ± 11.9a 59.3 ± 12.8c 44.8 ± 11.7ab 26.3 ± 11.9b 75.0 ± 21.5a 44.8 ± 12.5b 68.4 ± 19.5bc 25.1 ± 8.9ab 50.3 ± 13.9a 33.3 ± 6.9b 0.000 52.5 ± 11.8c 0.000 33.5 ± 6.6ab 0.003 Note: BR – bare-rooted, B&B – balled and burlapped, RP – root-pruned, AP – air-potted, FC – fabric container. Means within a column followed by a different letter are significantly differed from each other at 0.05 level using Tukey’s test. methods. For both species, the trees that were not exposed to any fine-root stimulating measures had the lowest amount of total fine-root length. There were however also differences between the fine-root stimulating production methods (i.e., the pre-establishing systems). RP sweet cherry trees had the highest total fine-root length and the AP sweet cherry trees had 83% of their total length of fine roots. FC sweet cherries had 37%, compared to the RP trees. Red oak RP trees had only 29% of the amount that the AP red oak trees had and FC red oak trees had 59% of the AP trees length. For both species, the fraction of 0.4–0.6 mm seemed to have the highest number of fine roots. Since only two trees from each group were used for the root studies, the observations can only indi- cate tendencies and give background information. DISCUSSION Transplant stress has been defined as a temporary condition of distress during which the plant experiences impaired functions caused by the handling of the plant, from the lifting in the nurs- ery to the planting into new, and often less favorable, growing conditions (Rietveld 1989). The definition also includes a period of recovery and adaption to the new environment. It is also stated that some degree of stress is inevitable, even under ideal plant- ing conditions. The results from this study are well in line with the definition, since post-transplant shoot growth of all trees in this study was negatively affected by transplanting, irrespec- tive of the production method, site, or species. The impaired functions manifested as very low shoot growth during the first two post-transplant years for trees of both species at both sites, compared to the pre-transplant growth of the undisturbed trees. Rietveld (1989) also states that the outcome of the stress depends on the interactions between the plant performance potential and the site conditions. In this study, the severity, in terms of reduced ©2013 International Society of Arboriculture
September 2013
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